LONDON • Pro-Brexit politicians in Prime Minister Theresa May's Conservative Party have launched a rival plan for leaving the European Union in an effort to force her to ditch her own blueprint in favour of a cleaner break with the bloc.

Former Brexit secretary David Davis, who quit in July because he disagreed with Mrs May, is backing the proposal published by the Institute of Economic Affairs (IEA) think-tank, which recommends preparing a "more aggressive" strategy for the EU negotiations, and opening trade talks with other countries around the world.

The timing was unfortunate for Mrs May, who headed into a potential Cabinet showdown yesterday. How the Prime Minister emerges - further weakened or limping on - is a key question after last week's bruising put-down by EU leaders.

Her defiant response last Friday has given her little respite, with speculation about challenges to her leadership and The Sunday Times reporting plans for a possible snap election in November.

Meanwhile, in Liverpool, the main opposition Labour Party is creating a different kind of Brexit problem for the Prime Minister by leaving the door open to supporting a second referendum on Brexit.

It is something that Mrs May gets asked repeatedly and last Friday outright rejected.

Delegates at Labour's annual conference will vote today on a motion that reads: "If we cannot get a general election, Labour must support all options remaining on the table, including campaigning for a public vote."

The group campaigning for a second referendum said it represents "clear movement" from the Labour Party towards another vote, though Shadow Chancellor John McDonnell said in a Bloomberg TV interview yesterday that there would be no option to stay in the EU.

"We will respect the referendum result that took place, but if we can't get a general election we'll campaign for a people's vote, and in that people's vote, people will be able to make a decision on the deal the government has brought back," Mr McDonnell said, adding that he does not expect Mrs May to deliver an agreement that Parliament would approve.

In a week's time, the Conservatives will hold their own annual conference, where the topic of Brexit will once again dominate.

Ahead of that meeting, Brexiteers have published their own proposal.

To unblock negotiations, Britain could propose a stripped-down "basic free trade agreement (FTA)" with the EU for goods, allowing more time to work on a better deal during the two-year transition period that will follow Brexit day in March, according to the IEA plan.

"The opportunity before the UK as a result of Brexit is huge: but if we squander it, the 'new normal' of limited economic growth will prevail, with an EU system that is failing to respond to the challenges of the modern economy," it said.

"The UK running its own economy will not render a deal with the EU impossible. It will bring back real growth, let the UK do other trade deals, and create leverage to get positive results from EU negotiations," it added.

But Mrs May's spokesman ruled out moving towards an FTA, saying it could not prevent a hard border on the island of Ireland - one of the main sticking points in negotiations with Brussels.

"The FTA would only apply to the Great Britain-EU relationship, with Northern Ireland effectively remaining in parts of the single market and Customs union," he said.

"The PM has repeatedly set out that we must protect the economic and constitutional integrity of the United Kingdom as a whole."

BLOOMBERG, AGENCE FRANCE-PRESSE