No-deal Brexit 'very likely', Barnier warns

He also warned that to avoid that no-deal scenario, the deal he and Theresa May negotiated is the only option. "If we were to avoid a no deal Brexit, there is only one way forward, to vote for a deal, if the UK wants to leave an orderly fashion," he told MEPs in Brussels.

On Monday evening, all four options put to the House of Commons to break the Brexit stalemate were rejected by MPs. The customs union motion was rejected by a margin of only three votes, while a second Brexit referendum fell short of a majority by 12 votes.

Barnier said the third option is a long extension to the Article 50 withdrawal procedure, but that would require "a strong justification", and for the UK to hold European elections in May.

The UK is set to leave the EU on 12 April. In case lawmakers in London do finally vote for the withdrawal agreement, a short delay would then be available until 22 May to prepare the necessary legislation.

A long extension, however, would likely be only granted by the EU if the UK either calls for a second referendum or holds a general election.

Barnier, in a speech earlier on Tuesday in Brussels, also added the possibility that British MPs need more time to look in detail again at the political declaration on the future relationship - an EU codeword for a closer EU-UK relationship with perhaps customs union or even single market included.

However, he also warned that a long extension beyond the month of May "would carry significant risks for the EU and therefore strong justification would be needed".

The EU is concerned that if the UK continues to be a member of the EU after the European elections, it could influence key decisions on top EU positions, such as the presidency of the EU commission, and the long-term EU budget.

In case of a long extension, the EU would require the UK to provide some guarantee that that decisions of the 27 will not be blocked by Britain. That guarantee would have to be "as binding as possible", a senior EU diplomat said.

Barnier said that such a UK, half-way out the door, "could pose a risk on our decision-making autonomy". The French politician also said that European businesses warned Brussels "against the cost of extending uncertainty".

A 'long' extension can be nine to 12 months, the diplomat said, but adding that the "bar is quite high" for the EU to grant such a delay.

Barnier again warned that the key issues of the withdrawal agreement - citizens' rights, financial obligations and the Irish border - will no go away in the case of a no-deal crash out of the bloc.

Barnier confirmed that when the UK asks the EU to begin negotiations on a future trade deal, sorting out these three issues will be a condition to launching new talks.

"A lack of a deal means a lack of faith, a lack of a deal means a rupture in trust between us. And I think we have to have trust in order to build the future relationship," Barnier said.

Border hurdle

The key hurdle will remain to keep the border on the island of Ireland open, while policing the new EU external frontier there to protect the single market.

Irish prime minister Leo Varadkar is in Paris on Tuesday, and German chancellor Angela Merkel will travel to Dublin on Thursday for talks on the issue.

Dublin has pledged not to introduce checks on the border between Northern Ireland and the Republic of Ireland to maintain the 1998 peace agreement that brought an end to violence in the region.

However, fellow EU countries are increasingly worried about a possible breach in the bloc's internal market and said checks will have to be set up.

Commission and Irish officials are working on identifying measures that could be put in place immediately after Brexit to check standards, and collect tariffs, as the UK leaves the bloc's single market.

"There would be immediate measures, not necessarily long term solutions, and not perfect, but a sort of degraded version of the backstop, that would concern only Ireland," the EU diplomat said.

The diplomat dismissed ideas that checks would not be done on the island, and only on products going to Europe's mainland would be policed. He said the EU's goal is to also protect Irish citizens and consumers as well, as guaranteed by EU law.

The EU is gearing up its preparations for a no-deal Brexit, but also started to prepare the ground in Europe, admitting there will be disruptions on the European side as well.