Tom Tugendhat suggests Britain could withdraw by 24 August but No 10 says idea not under consideration

A senior Conservative MP has raised the idea that Boris Johnson could unilaterally withdraw the UK from the European Union in the next 10 days to try to avoid attempts by parliament to block a no-deal Brexit.

Tom Tugendhat, who chairs the Commons foreign affairs committee, put forward a possible chronology of a unilateral withdrawal by 24 August followed by an immediate general election, with the Irish border issue then solved by a Northern Ireland-only backstop.

A Downing Street source said the idea was not under consideration, and one expert in EU law said the withdrawal date could only be changed with the consent of Brussels.

The plan, if carried out, would be hugely controversial, and would take companies and the financial markets by surprise before no-deal preparations had been completed.

However, Tugendhat, the MP for Tonbridge and Malling, is a respected and well connected backbencher. He was among 20 Conservative MPs, alongside the former chancellor Philip Hammond, who have written to Johnson accusing him of setting the bar too high in negotiations with the EU to have a hope of getting changes to a deal.

In a tweet, Tugendhat asked:

Tom Tugendhat (@TomTugendhat) What odds would you give on:

1 UK exits EU by 24 Aug - in time for G7 or before Parliament returns. Art 50 passed so nothing to stop unilateral withdrawal.

2 General Election straight after to get majority.

3 Answer Irish border Q with NI only referendum on NI only backstop?

In response to tweeted questions about the repeated objections by the Democratic Unionist party to any regulatory provision that applied only to Northern Ireland, Tugendhat argued that a Johnson government could ignore this if it won a majority in the subsequent election, and that a referendum would give the idea credibility.

Such a plan, particularly the idea of unilateral withdrawal without any warning followed by an immediate election, would seem hugely politically risky, and could prompt a furious reaction from MPs, businesses and many members of the public.

However, No 10 is known to be concerned that the Commons could find a way to block Johnson’s much-promised departure by 31 October if it involved leaving the EU without a deal, whether through taking control of the parliamentary order paper or means such as a no-confidence vote in the government.

Steve Peers, a professor of EU law at the University of Essex, said he did not think such a plan was feasible. While changing the date of withdrawal could be done via so-called secondary legislation, not voted on by MPs, he tweeted, the EU Withdrawal Act states it must happen “in accordance with article 50(3) of the Treaty on European Union”, which sets out the EU’s constitutional basis.

Section 50(3) of the treaty says an extension to the standard two-year wait for departure under article 50 can only take place if “the European council, in agreement with the member state concerned, unanimously decides to extend this period”. This indicated any change of date would need agreement, he said.

Peers wrote: “So the EU would have to agree to change the date. ‘Unilateral’ change of date is therefore illegal.”