Theresa May must stop banging her head against a brick wall over Brexit, Tony Blair has urged, as he reiterated calls for a second referendum.

The former prime minister described Britain’s withdrawal from the EU as a “man made” issue which can be “unmade by man”, and called on European leaders to begin preparing for an extension to the UK’s membership.

Mr Blair suggested Mrs May should take her “head off the brick wall and think creatively”, and claimed there was at least a 50% likelihood of another referendum – saying it would be “undemocratic” to deny people a second vote.

Following a speech in central London on Friday morning, the former Labour leader said: “My advice to the Prime Minister is very simple – I actually think funnily enough she could still play a role in this if she just decided that given the fact there isn’t a majority for any form of Brexit she could facilitate a chance for everyone to vote on the options.

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Tony Blair has called for a second referendum on Brexit (Stefan Rousseau/PA)

“It’s not that hard as a prime minister to say ‘look I’ve done my best, I’ve tried my level best, I’ve been negotiating for two-and-a-half years, I’ve done everything I possibly can to reach an agreement, I’ve listened to you and I’ve listened to you and I’ve tried to square the circle – I can’t.

“And what I’ve come up with is the best that I can come up with and you, Parliament, rejected it so you the British people now must decide what we’re going to do…

“My advice to her is there’s no point literally in carrying on banging your head against this brick wall. It’s sensible to take your head off the brick wall and think creatively.”

He said the country had been “held hostage” by a division in the Tories, but said the issue was such that it would not make any difference if it was a Labour or Conservative government “or a divine government” running the negotiations.

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Former prime minister Tony Blair has urged Theresa May to accept her Brexit deal will not be passed (Stefan Rousseau/PA)

Mr Blair described the “disentangling” process of Brexit as “hideously complex” and said all options of leaving the EU have “significant drawbacks” compared with staying in.

He said the only way of maintaining a frictionless border between Northern Ireland and the Republic was by ensuring the two are in the same trading system.

And he issued a rallying cry to MPs, saying: “This is a moment when if you’re a politician, if you’re an ordinary Member of Parliament, for once in your political life you actually hold the destiny of a nation and the fate of a people in your hands.

“For once you’re able to rise above all that drudgery of politics and make a big decision. So make the big decision on the basis please of what you think is right.”