LONDON — British Prime Minister Theresa May has warned that her Brexit plan is the only alternative to crashing out of the European Union without agreement, in an interview broadcast on Monday.

Despite strong opposition in her Conservative party and criticism in Brussels, May has stuck by the so-called Chequers proposal to keep close trade ties with the EU after Brexit on March 29 next year.

“The alternative to that will be not having a deal,” she said.

May will meet EU leaders in Salzburg on Wednesday and Thursday, as she seeks a breakthrough in talks on the Brexit divorce and the future UK-EU trading relationship.

Even if she gets a deal in the coming weeks, it must be agreed by the House of Commons in London, where she has only a small majority.

A senior figure in the main opposition Labour party has said it was likely to vote against the deal, meaning only a small number of May’s Conservative MPs need rebel to kill it.

May expressed confidence parliament would approve the deal — but warned there was no alternative if Britain wanted to avoid a potentially disruptive “no deal” scenario.

“Do we really think... that if parliament was to say, ‘No, go back and get a better one’, do we really think the EU is going to give a better deal at that point?” she said.

May has proposed that Britain follow EU rules in trade in goods after Brexit, to protect manufacturing supply lines and avoid a “hard border” between Northern Ireland and Ireland.

“I don’t want manufacturers to feel that they’ve got to operate under all sorts of different rules, because that complicates life for them and that potentially means business leaving this country,” she said.

May also insisted no other plan on the table would ensure “frictionless” trade in Ireland.

But critics say her proposal would tie Britain too closely to the EU, and argue that the Irish issue can be resolved through trusted trader schemes and the use of technology.

Former Foreign Minister Boris Johnson, who quit in July in protest at the Chequers plan, launched a fresh attack on it in his weekly newspaper column on Monday.

“The whole thing is a constitutional abomination,” Johnson, who has previously compared the plan to a “suicide vest”, wrote in the Daily Telegraph.

Meanwhile, the International Monetary Fund warned on Monday saying that Britain’s economy would suffer “substantial costs” should it leave the European Union in March with no divorce agreement.

Brussels and London have failed to resolve “fundamental” aspects of Brexit and this could leave London defaulting to World Trade Organization (WTO) tariffs, the IMF said in its annual outlook on the UK economy.

“Fundamental questions — such as the future economic relationship between the two and the closely-related question of the status of the land border with Ireland — remain unanswered,” the institution noted in a statement.

“Resolving these questions is critical to avoid a ‘no-deal’ Brexit on WTO terms that would entail substantial costs for the UK economy — and to a lesser extent the EU economies — particularly if it were to occur in a disorderly fashion,” the IMF added. — AFP