DONALD Tusk has warned there can be "no frictionless trade" with the EU if the UK is outside the customs union and single market.

"Friction is an inevitable side-effect of Brexit by nature," the European Council President told business leaders in Brussels just hours before he is due to hold a bilateral meeting with Theresa May in Downing Street.

A "hard border on the island of Ireland" was one of the "possible negative consequences" of the kind of Brexit set out by the UK's red lines, Mr Tusk insisted.

He said he would ask the Prime Minister at their meeting in London whether or not the UK had "a better idea that would be as effective in preventing a hard border" as that set out in Brussels' draft withdrawal agreement, which was categorically rejected as unacceptable by her yesterday.

Irish senator Neale Richmond, European Affairs spokesman for the Fine Gael party that leads the Dublin Government, said Britain had provided "zero detail" on its proposed alternatives to keeping Northern Ireland in a customs area with the EU to avoid a hard border with the Republic of Ireland.

He told BBC Radio 4's Today programme: "We are very, very hopeful that an overarching, overall trading and customs agreement [for the whole UK] can be reached.

"However, the British Government has stressed there are alternative options and imaginative options, that's well and good and fine and[on] the European side, we are of course prepared to look at that, but we have seen zero detail about those."

Mr Richmond also dismissed Boris Johnson's suggestion that crossing the Irish border could be managed in a similar way to the congestion charge in London, without the need for physical checks.

"You are talking about two boroughs that are in the same customs union, that are in the single market, that didn't have an armed conflict in the last 20 years - it is an absolutely ridiculous suggestion that is not comparable to the situation on the island of Ireland," he said.

Mrs May is facing a frenetic 48 hours of Brexit diplomacy as she tries to secure a united Cabinet ahead of her talks with Mr Tusk and a keynote speech on the UK's future relationship with the EU due to take place tomorrow in north-east England.

The PM has strongly rejected parts of a draft legal text from the European Commission regarding the post-Brexit status of Northern Ireland, which she said would "threaten the constitutional integrity of the UK" by creating a border down the Irish Sea.

Meanwhile, Tony Blair claimed the PM’s Brexit plan was "literally not going to happen" no matter how tough she was in negotiations with the European Union.

The former Prime Minister said Britain was no further forward nearly a year after triggering Article 50 to start negotiations.

He said there was a fundamental dilemma at the heart of Brexit which there was "no way round"; the UK could either leave the single market and customs union to take control of its laws but take an economic hit and a hard border in Northern Ireland or stay in and keep a frictionless frontier and easy trade with the EU.

Less than 24 hours after Sir John Major branded the PM’s approach to Brexit as “grand folly,” Mr Blair defended his predecessor as PM, who argued that MPs should have a free vote on the final deal with the option of putting it to the public in a second referendum.

The former Labour leader described Sir John’s intervention as "heartfelt" and "analytical".

Ahead of his own speech in which he will urge European leaders to help stop Brexit by promising new measures to address concerns on immigration, Mr Blair told Today: "The problem that she has is that there is no way round the dilemma.

"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."

Mr Blair repeated his criticism of Brexiteers, who dismissed 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 declared.

He said Jeremy Corbyn's commitment to a customs union with the EU to maintain a soft border and maintain tariff-free trade was "sensible" but warned Labour would "very soon find that we've got to move further in order to escape the dilemma ourselves".

The ex-premier was visiting Brussels to ask for assistance in preventing the UK's departure from the EU, telling the continent's leaders they share the responsibility to "lead us out of the Brexit cul-de-sac".

Mr Blair will argue that the British people should be given a final say on the Brexit deal and if EU leaders offer further concessions, the public could change its mind on leaving the bloc.

He will set out three steps which could lead to a "reconsideration of Brexit":

*demonstrate to the British people that what they were told in June 2016 "has turned out much more complex and costly than they had thought";

*show there are better ways to respond to the "genuine underlying grievances beneath the Brexit vote, especially around immigration" and

*say EU leaders should accept the Brexit vote is a "wake-up call" to change and "not just an expression of British recalcitrance"

Mr Blair will tell the European Policy Centre think-tank: "Reform in Europe is key to getting Britain to change its mind."

He will call for "a comprehensive plan on immigration control, which preserves Europe's values but is consistent with the concerns of its people and includes sensitivity to the challenges of the freedom of movement principle".