TONY Blair has urged European Union leaders to work to lead Britain out of the “Brexit cul-de-sac,” warning them the UK could act as a focal point of disunity once outside the bloc.

The former prime minister said Brexit would not only damage the economy of the UK but also the EU’s, weakening its "standing and power" on the world stage.

He called for reform - particularly to deal with concerns on immigration - as a way of persuading British voters to reverse Brexit.

In a speech in Brussels, Mr Blair said the economic cost of Brexit to the rest of the EU would be "significant and painful".

He warned: "Britain out of Europe will ultimately be a focal point of disunity, when the requirement for unity is so manifest. No matter how we try, it will create a competitive pole to that of Europe, economically and politically to the detriment of both of us.”

Stressing how it was "better to make our future work together," the former PM argued that the anxieties which led to the Brexit vote were being felt all over Europe.

“They're not specific to the British. Read the latest Eurobarometer of public opinion. In many countries, similar referendums might have had similar results,” he declared.

The ex-PM pointed to French President Emmanuel Macron’s proposal for a series of Europe-wide debates on the continent’s future in recognition of the strains in its politics.

“These will not work, however, if they become merely a way of explaining to Europe’s citizens why their worries are misplaced. It should be a real dialogue. The populism convulsing Europe must be understood before it can be defeated,” he argued.

On immigration, Mr Blair said there was a genuine fear, which could not be dismissed.

Many, he argued, felt the European project was too much directed to the enlargement of European institutions rather than to projects, which would deliver change in people’s daily lives.

Calling for a comprehensive plan on immigration control, which preserved Europe’s values but also addressed the concerns of its people, the former party leader said reform was the key to getting Britain to change its mind.

“If at the point Britain is seized of a real choice, not about whether we like Europe or not – the question of June 2016 – but whether on mature reflection the final deal the British Government offers is better than what we have, if, at this moment, Europe was to offer a parallel path to Brexit of Britain staying in a reforming Europe, that would throw open the debate to transformation.”

He added: “People will say it can't happen. To which I say in these times in politics anything can happen.”