Members of UK Prime Minister Theresa May’s Conservative Party could move to resign en masse if the UK is forced to take part in European elections next month and extend its EU membership beyond the end of June.

Conservative lawmakers, among others, are becoming increasingly concerned as the third day of negotiations between May and the opposing Labour Party ended with no clear plan for the future. The prime minister has been warned that ministers of her cabinet have reportedly been discussing a mass resignation if May accepts a delay that would have Britain participate in the European Elections, the Sunday Telegraph reported.

Meanwhile on Saturday, May acknowledged that the government's strategies to get her Brexit deal approved in Parliament failed, saying there's little prospect lawmakers will back the thrice-rejected divorce agreement "in the near future."

The previous three days of talks ended with no agreement, with Labour accusing May's Conservative government of not offering any compromise on their plans.

"I haven't noticed any great change in the government's position so far," Labour leader Jeremy Corbyn said Saturday. "I'm waiting to see the red lines move."

May, however, announced in her Saturday statement that she has “no choice but to reach out across the House of Commons,” as a longer delay could risk the UK not leaving at all.

"The referendum was not fought along party lines and people I speak to on the doorstep tell me they expect their politicians to work together when the national interest demands it," she said, adding that risking the UK staying would mean “letting the Brexit the British people voted for slip through our fingers.”

The British prime minister said that the two main parties want to respond to the people’s demands and end free movement, leave the European Union with a good deal and protect jobs.

READ MORE: May Says Brexit Choice Narrowed to Leaving EU With Deal or Remaining in Bloc

According to the Sunday Times, May's government has a plan to enshrine in law a customs arrangement with the European Union in a bid to win over the opposition Labour Party to back a Brexit deal.

"Under the new plan, the prime minister would offer to rewrite the government's withdrawal bill to enshrine a customs arrangement in law," the newspaper said, quoting unnamed sources.

The UK is due to leave the EU on 12 April and, as yet, no withdrawal deal has been approved by the House of Commons and it is unclear whether the EU would allow another extension of the deadline and how long it would be.