Michel Barnier told to plan for second Brexit referendum as Final Say petition approaches one million signatures

Chief negotiator was told to consider Article 50 extension in Brussels meeting

The EU’s chief negotiator has been warned to make contingency plans for a second Brexit referendum, as pressure builds to give the public a final say on leaving.

Prominent Remain politicians met with Michel Barnier in Brussels this week and said it was time to start “serious contingency planning”, as The Independent’s petition neared one million signatures and the future of Brexit looks increasingly uncertain.

In a visit on Friday, Sadiq Khan, the mayor of London, told Mr Barnier that the negotiating period should be extended so Britain could have “time to have a referendum”.

The warning comes after 700,000 people took to the streets of London last weekend to make the case for a vote on the final deal.

For there to be time to hold a referendum, the EU would likely have to extend the Article 50 negotiating period, which will automatically expire on 29 March 2019, leaving Britain to slide out with a no-deal Brexit.

The calls for an extension came from across a number of parties.

Liberal Democrat leader Vince Cable said following a meeting with Mr Barnier on Thursday: “My message to Michel Barnier was clear: it’s time to start serious contingency planning for a People’s Vote. We know the UK government has started making such plans as a result of the growing demand for such a vote, demonstrated by last weekend’s march.

“The EU should do the same, because MPs who back the People’s Vote are fast forming the biggest and most cohesive bloc in Westminster.”

Plaid Cymru Westminster group leader Liz Saville Roberts, who also met with Mr Barnier, said she had used the meeting to push for an extension to the negotiation period to accommodate a referendum.

“I pressed Michel Barnier on protecting Wales’s interest through the extension of Article 50 and a People’s Vote,” she said.

“In Westminster, with the prime minister’s proposals amounting to nothing more than a mix of fudge and fantasy, a People’s Vote is more likely than ever.”

The EU has previously reacted cooly to suggestions that the period could be extended, but has not ruled it out. An extension would require the unanimous approval of all 28 EU leaders on the European Council.

Sadiq Khan visited Brussels on Friday (Getty)

Brussels is particularly wary about extending the transition into May, when Britain would have to take part in the next European Parliament elections if it was still in the EU.

Mr Khan, speaking after a separate meeting on Friday, said: “The point I made to Michel Barnier, really quite forcefully, is that there is a possibility of the British parliament rejecting the deal that Mrs May secures from the EU.

“There is a very real possibility of there being either a general election, which I think is less likely, or a referendum. In those circumstances, I suggested the EU should begin preparatory work on the extension of Article 50.

“Because what would not be a good thing in my view is if we managed to get a referendum but it was too late because we had left the EU or the EU had not made preparations for an Article 50 extension.”

Mr Khan added: “Whatever Theresa May brings back will probably be rejected by cabinet, almost certainly rejected by the party, and if not will definitely be rejected by parliament.

“That’s why I said to Michel Barnier: listen, you need to start preparing for the possibility of extending Article 50 because if that is the case we will need time to have a referendum.”