Sadiq Khan has made a last-gasp plea for Britons to be able to keep EU citizenship despite Brexit – as the best way for the country to be “reconciled”.

The idea, long advocated by some senior figures in Brussels, would help people left “heartbroken” by departure from the European Union, the mayor of London said.

It would allow British citizens to retain the right to free movement between EU member states after the end of the transition period, in December, as well as voting rights for the European parliament.

Mr Khan put the plan forward as he prepared to meet Michel Barnier, the EU’s Brexit negotiator, and after the two sides stepped up their war of words before trade talks begin.

“I am heartbroken that we are no longer a member of the European Union, but that doesn’t mean our country’s future can’t be closely linked with the rest of Europe,” he said.

“The prime minister says his job is to bring the country together and move us forward and I cannot think of a better way of reconciling the differences between British voters who wanted to leave, and the millions of Londoners and British nationals who still feel and want to be European.

“There would be support from millions of Londoners and British nationals who are devastated they are losing their rights as EU citizens.

“As the UK and EU start their next phase of negotiations, I want this issue of associate citizenship to be at the heart of talks about our future relationship.”

Guy Verhofstadt, the European parliament’s Brexit coordinator before the UK’s departure, has long campaigned for “associate citizenship” for people angry at losing EU privileges.

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(Photo by Glyn KIRK / AFP) (Photo by GLYN KIRK/AFP via Getty Images) GLYN KIRK AFP via Getty Brexit day: UK says goodbye to EU A man wears a pro-Brexit t-shirt Reuters Brexit day: UK says goodbye to EU Anti-Brexit demonstrators visit Europe House to give flowers to the staff on Brexit day Reuters Brexit day: UK says goodbye to EU Pro Brexit supporter wears a novelty Union Jack top hat outside the Houses of Parliament Getty Images Brexit day: UK says goodbye to EU Customers Scott Jones and Laura Jones at the Sawmill Bar in South Elmsall, Yorkshire, where a Brexit party is being held throughout the day PA Brexit day: UK says goodbye to EU A pro-Brexit demonstrator clenches his fist during a rally in London, Friday, Jan. 31, 2020. Britain officially leaves the European Union on Friday after a debilitating political period that has bitterly divided the nation since the 2016 Brexit referendum. (AP Photo/Alberto Pezzali) Alberto Pezzali AP Brexit day: UK says goodbye to EU LONDON, ENGLAND - JANUARY 31: Pro-EU activists protest at Parliament Square as people prepare for Brexit on January 31, 2020 in London, United Kingdom. At 11.00pm on Friday 31st January the UK and Northern Ireland will exit the European Union 188 weeks after the referendum on June 23rd 2016. (Photo by Jeff J Mitchell/Getty Images) Jeff J Mitchell Getty Brexit day: UK says goodbye to EU LONDON, ENGLAND - JANUARY 31: Pro Brexit supporters hold up placards at Parliament Square as people prepare for Brexit on January 31, 2020 in London, United Kingdom. At 11.00pm on Friday 31st January the UK and Northern Ireland will exit the European Union 188 weeks after the referendum on June 23rd 2016. (Photo by Jeff J Mitchell/Getty Images) Jeff J Mitchell Getty Images Brexit day: UK says goodbye to EU Pro-EU activists protest Getty Images Brexit day: UK says goodbye to EU A pro-Brexit demonstrator burns a European Union flag AP Brexit day: UK says goodbye to EU Pro Brexit supporters Getty Images Brexit day: UK says goodbye to EU Pro Brexit supporters Getty Images Brexit day: UK says goodbye to EU A Brexit supports holds a sign in Parliament Square AP Brexit day: UK says goodbye to EU A man carries an EU themed wreath Reuters Brexit day: UK says goodbye to EU Ann Widdecombe reacts with other members of the Brexit party as they leave en masse from the European Parliament PA Brexit day: UK says goodbye to EU Anti-Brexit demonstrators in Parliament Square PA Brexit day: UK says goodbye to EU Pro EU supporters let off flares from Westminster Bridge Getty Brexit day: UK says goodbye to EU British MEPs Jonathan Bullock, holding the Union Jack flag and Jake Pugh leave the European Parliament, in Brussels on the Brexit day AFP via Getty Brexit day: UK says goodbye to EU Newspapers and other souvenirs at a store, near Parliament Square Reuters Brexit day: UK says goodbye to EU Brexit supporters hold signs in Parliament Square AP Brexit day: UK says goodbye to EU Pro-EU protesters hold placards in Parliament Square AFP via Getty Brexit day: UK says goodbye to EU French newspapers PA Brexit day: UK says goodbye to EU Sinn Fein leader Mary Lou McDonald with a Border Communities Against Brexit poster before its unveiling in Carrickcarnon on the Irish border PA Brexit day: UK says goodbye to EU National growers organisation British Apples & Pears has renamed a British apple to EOS, the Greek goddess of dawn, to commemorate Brexit day AP Brexit day: UK says goodbye to EU Pro-EU protesters hold placards in Parliament Square AFP via Getty Brexit day: UK says goodbye to EU Britain's departure from the European Union was set in law on January 29, amid emotional scenes, as the bloc's parliament voted to ratify the divorce papers. 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But neither Theresa May nor Boris Johnson has shown any interest in the idea, the latter insisting free movement will end for all UK citizens at the end of the year.

Mr Verhofstadt said: “The Maastricht Treaty created the concept of ‘European citizenship’ and I am in favour of using this now as a basis for people who want to keep their link with Europe.

“It is the first time in the history of our union that a member state leaves, but it is not because the UK government wanted exit that individual citizens have to lose their connection with the continent.”

But Rory Stewart, the former Conservative candidate running as an independent in May’s mayoral election, attacked the policy as “only a sound bite”.