2.3.1 – The Main Powers of the Executive
Ordering military action is one of the most momentous decisions a Prime Minister has to make, albeit one they hope to never have to do so. So, why is it their decision and what role does Parliament have in it?
Under what power is military action ordered?
One of the Monarch’s ancient prerogative powers is that they are Commander-in-Chief of the British Armed Forces and make the relevant decisions about their deployment. However, since the 17th Century this power, like many other royal powers, has transferred to the government and, in the case of military deployment, to the Prime Minister.
Parliament is also sometimes given a role in deciding whether or not military action should be taken. However, this role is not constitutional, it is bestowed upon Parliament by the Prime Minister, if they wish to do so. It was believed that after 2003 this may have become a constitutional convention but events since have shown this not to be the case.
Why did Parliament vote on military action in 2003?
Traditionally, the Prime Minister has not had to ask Parliament for permission to deploy military forces overseas. However, the Iraq War seemingly set a precedent that Parliament needed to be consulted before military deployment. Before launching the invasion of Iraq in March 2003 the government of Tony Blair presented their evidence to the House of Commons and allowed the house to vote on military intervention in the country.
Even though Robin Cook invoked the doctrine of collective responsibility and resigned from the government, the House of Commons voted to support military action by 412 to 149 votes. The Conservative opposition supported the action and the invasion of Iraq took place on the 19th March 2003.
On what other occasions has military action been taken since 2003 and have Parliament had a say?
It has appeared to be a growing convention that the Government seeks approval from Parliament for engaging in military action, however, this has not always been a clear picture as the range of military interventions have shown:
Kosovo (1999) – Tony Blair talked strongly of the ‘Responsibility to Protect’ that the world’s most powerful countries have. This was put nowhere more strongly than in his famous Chicago Speech of 1999, which was aimed at the US President, Bill Clinton, as atrocities took place in Kosovo.
Britain took part in a NATO Bombing campaign that lasted from March to June 1999. This was aimed at forcing Serbian troops from Kosovo and to protect Kosovan refugees.
In this case, Parliament was not consulted before military action was launched. A bid was made by 13 Labour MPs to force a vote, but this was unsuccessful.
Sierra Leone (2000) – In May 2000 British troops were deployed to Sierra Leone to protect civilians who were evacuating key areas. As a former British colony, Britain felt a moral responsibility to intervene. British intervention helped to calm the situation in the country until a UN Resolution (1313) authorized an increasing number of UN peacekeepers.
Parliament was not consulted before troops were deployed to Sierra Leone.
Afghanistan (2001) – On September 11th 2001 the world watched as America came under attack from Al-Qaeda. The terror group, led by Osama Bin Laden, were harboured by the Taliban government in Afghanistan. Britain joined the United States and other NATO countries in invading Afghanistan to remove the Taliban and Al-Qaeda. British troops remained active in Afghanistan until 2014.
Whilst the issue was debated in Parliament, there was no formal vote before British forces were committed to military action
Libya (2011) – Under UN Security Council Resolution 1973 Britain joined France and the US in conducting air strikes against the forces of Libyan dictator Muammar Gaddafi. The stated aim of the operation was to protect civilians at risk during the ongoing civil war.
The action was put to a vote in Parliament and passed by 557-13.
Syria (2013) – David Cameron advocated for action in Syria in response to the use of chemical weapons by President Assad. Alongside the United States, he believed a strong response was needed to ensure the global community recognised that the illegal use of chemical weapons would not be tolerated.
The action was put to a vote in the House of Commons and Cameron was defeated by 285-272. This was the first time a Prime Minister had lost a vote on military action since 1782.
Iraq (2014) – David Cameron advocated for action in Syria and Iraq to tackle the rise of the Islamic State of Iraq and Syria (ISIS).
Parliament debated this and voted in favour by 524 to 13.
Syria (2015) – In a similar operation to Iraq, Cameron said that air strikes were needed to stop the spread of ISIS in Syria.
After a 10-hour debate, Parliament voted in favour of this action by 397-223. The operation continues to this day.
This debate was particularly tricky as the Labour Party were divided over the issue. For example, the leader, Jeremy Corbyn, was opposed to air strikes while his Shadow Foreign Secretary, Hillary Benn, was in favour. As it was a free vote, collective responsibility was suspended.
Syria (2018) – Theresa May took action against the Assad regime in Syria due to the use of chemical weapons. However, unlike Cameron in 2013, May did not seek the authorisation of Parliament for action, saying the airstrikes were both ‘right and legal’.
In response to this, Labour Leader Jeremy Corbyn called for a War Powers Act to be passed that would ensure that Parliament would have to be consulted before military action was taken:
“I think parliament should have a say in this, and the prime minister could quite easily have done that…What we need in this country is something more robust, like a war powers act, so that governments do get held to account by parliament for what they do in our name.”
Action against Houthi Rebels (2023) – In January 2023 Rishi Sunak ordered British forces to conduct air strikes against Houthi Rebels in Yemen. The Houthis are supported by Iran, who also support Hezbollah in Lebanon and Hamas in Gaza. Recently, Houthi forces in Yemen have attacked commercial shipping in the Red Sea which the say his heading to Israel. This has led to commercial shipping avoiding using the Red Sea and instead detouring around the Cape of Good Hope. The Red Sea is a significant trade route and the Suez Canal that connects it to the Mediterranean carries around 10% of all seaborne oil transported anywhere in the world. There was, therefore, both an economic and strategic imperative to the action.
Rishi Sunak did not put this action to a vote in the House of Commons.
Should the UK Parliament be consulted on military action?
It is a matter of debate as to whether Parliament should be consulted on military action and that a ‘War Powers Act’ should be passed.
Arguments in favour include:
- Democratic accountability: Holding a vote in Parliament ensures that decision taken has democratic support. In a liberal democracy, democratic support for a decision is always preferable.
- Public Trust: Debating issues of military action can enhance public trust in political institutions. This is particularly important at a time when trust in politics is very low.
- Legal considerations: There are often legal debates over military action. As Parliament is sovereign in the UK, a parliamentary result gives legal cover to any decision taken by a Prime Minister.
However, arguments against
- Speed: Often decisions on military action are urgent and need to be taken at speed. Asking parliamentary approval for all military action may negate the effectiveness of the action itself.
- Operational Necessity: The delay that may occur in seeking parliamentary approval may but an operation at risk and increase the risk to British military personnel.
- Politicisation: There is a danger that issues of immediate national security may be open to politicisation if they are put to a vote in Parliament.
Article Summary
The power to engage British forces in military action belong solely to the Prime Minister. It is what is called a Royal Prerogative power. At times Prime Ministers have chosen to seek consent from Parliament on military action, however, they do not have to.
Key Terms
War Powers Act – A potential Act of Parliament that would ensure that Parliament has the final say on military action.
Royal Prerogative Powers – Powers that traditionally belonged to the Monarch but are now exercised on their behalf by the government, especially the Prime Minister.
Collective Responsibility – A doctrine in UK politics which dictates that if a Minister or Shadow Minister cannot agree with their parties position on an issue they should resign.
Responsibility to Project – A doctrine in international law that dictates that states have not just a right, but a responsibility to intervene when a state has failed to protect its own citizens from human rights abuses.
Last Updated: 10th January 2026