British Prime Minister Theresa May's Brexit plan is "literally not going to happen" no matter how tough she is in negotiations with the European Union, Tony Blair says.
The former prime minister said Britain is no further forward nearly a year after triggering Article 50 to start negotiations.
Ahead of a major Brexit strategy speech, Blair also defended his predecessor John Major, who has said MPs should have a free vote on the final deal with the option of putting it to the public in a second referendum.
Ahead of his own speech in which he will urge European leaders to help stop Brexit, Blair told BBC Radio 4's Today program: "The problem that she (May) has is that there is no way round the dilemma.
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"What she thinks is that it's possible to get the European Union to give us access to Europe's markets without the same obligations that the rest of Europe has in the single market.
"That is not possible. It's not a question of a tough negotiation or a weak negotiation, it literally is not going to happen.
"So the dilemma you have is you're either going to have to stay close to Europe to minimise economic damage, in which case you abide by Europe's rules, or you're free from Europe's rules, in which case you're going to have economic damage."
Blair repeated his criticism of Brexiteers who dismiss the impasse in negotiations over maintaining a soft Irish border.
"I find it not just disappointing but sickening that people should really be prepared to sacrifice peace in Northern Ireland on the altar of Brexit," he said.
