Theresa May should not trigger article 50 alone – formally starting the UK’s exit from the European Union – without “explicit parliamentary approval”, a parliamentary committee has warned.

In a direct challenge to Downing Street’s authority over Brexit, the House of Lords constitution committee has published a report declaring that it would be “constitutionally inappropriate” for the prime minister to act on an advisory referendum without referring back to parliament.

The report says: “In our representative democracy, it is constitutionally appropriate that parliament should take the decision to act following the referendum. This means that parliament should play a central role in the decision to trigger the article 50 process, in the subsequent negotiation process, and in approving or otherwise the final terms under which the UK leaves the EU.

What is article 50 and why is it so central to the Brexit debate? Read more

“It would be constitutionally inappropriate, not to mention setting a disturbing precedent, for the executive to act on an advisory referendum without explicit parliamentary approval – particularly one with such significant long-term consequences. The government should not trigger article 50 without consulting parliament.”

The question of whether parliament or the prime minister has the authority to trigger article 50 is the central issue in the legal challenge against the government to be heard next month.



Article 50 itself merely states: “Any member state may decide to withdraw from the union in accordance with its own constitutional requirements.” It does not specify what the constitutional requirements are, an ambiguity which has allowed rival claims of authority to be advanced by parliament and the executive.



Ian Lang, the Conservative peer and chairman of the House of Lords constitution committee, said: “The referendum result was clear and it is right that the government are preparing to take Britain out of the EU. However, our constitution is built on the principle of parliamentary sovereignty and the decision to act following the referendum should be taken by parliament.

“Parliament should be asked to approve the decision to trigger article 50 – a decision which will start the formal process of the UK leaving the EU and set a deadline for the UK’s exit. Parliament’s assent could be sought by means of legislation or through resolutions tabled in both Houses of Parliament.



“An act of parliament would give greater legal certainty and could be used to enshrine the ‘constitutional requirements’ required by article 50, allowing for the setting of advantageous preconditions regarding the exit negotiations to be met before article 50 could be triggered. A resolution could be simpler and quicker to secure but might not provide the same watertight legal authority. We consider that either would be a constitutionally acceptable means of securing parliamentary approval for the triggering of article 50.”

The committee’s report concludes: “The referendum result was clear. Parliament is now responsible for ensuring that the government takes forward the complex process of negotiating the UK’s withdrawal from the European Union in a manner that achieves the best possible outcome for the UK as a whole. The focus must now be on how parliament and the government will work together to that end.

“That cooperation should start now. Parliament and the government should, at this early stage, take the opportunity to establish their respective roles and how they will work together during the negotiation process. The constitutional roles of each – the executive and the legislature – must be respected, beginning with parliamentary involvement and assent for the invoking of article 50.”

Disputing the House of Lords constitiution committee report, a spokesperson for the Department for Exiting the European Union said: “The government’s position is very clear. This is a prerogative power, and therefore one that should be exercised by the government.

“Parliament voted by a majority of six to one to give the British people the decision on our membership of the EU in a referendum.



“As the secretary of state for exiting the EU [David Davis] made clear to parliament this week, the triggering of article 50 is the beginning of the process of exit and we expect parliament to be fully consulted and engaged throughout.”