British Prime Minister Theresa May has revealed the details of her “new” Brexit plan after declaring that MPs have “one last chance” to vote on whether to hold a second referendum.

In an attempt to get her EU divorce deal through parliament, Ms May delivered new guarantees on workers’ rights, environmental protections, the Northern Irish border and a compromise on customs arrangements.

Ms May reportedly held a three-hour Cabinet meeting on Wednesday (Australian time) before delivering her speech titled ‘A new Brexit deal – seeking common ground in Parliament’.

She warned this was the last chance to avoid “a nightmare future of permanently polarised politics” and her deal would be guaranteed to last for “at least this Parliament”.

The newly devised plan comes just days before the European parliamentary elections. Support for the Brexit party, which backs a new referendum that would give voters the option of remaining in the EU, soared in the polls.

Three years since Britain voted to leave the EU and almost two months after the planned departure date, Ms May is mounting a last bid to try to get the deeply divided parliament’s backing for a divorce deal. This is her fourth attempt to break an impasse in parliament over Brexit.

“I say with conviction to every MP or every party: I have compromised, now I ask you to compromise,” Ms May said in a speech at the headquarters of PricewaterhouseCoopers.

“We have been given a clear instruction by the people we are supposed to represent, so help me find a way to honour that instruction, move our country and our politics and build the better future that all of us want to see.”

Despite offering what she described as “significant further changes”, many MPs, hardened in their positions, have already decided not to vote next month for the Withdrawal Agreement Bill, legislation which implements the terms of Britain’s departure.

By offering the possibility of holding a second vote on her deal and a compromise on customs arrangements, Ms May hopes to win over opposition Labour MPs, whose votes she needs to overcome resistance to the deal within her own Conservative Party.

But she will infuriate Brexit-supporting MPs, who have described a customs union with the EU as no Brexit at all.

Conservative MP Simon Clarke said he had backed Ms May’s deal during the third failed attempt in parliament, but “this speech from the PM means there is no way I will support the Withdrawal Agreement Bill”.

“So if we pass the Withdrawal Agreement Bill at 2nd reading, we allow a Remain Parliament to insist upon a 2nd referendum and a Customs Union? This is outrageous,” he said on Twitter.

Ms May’s movement towards what many describe as the “Remain” MPs, who want to stay in the EU, is a shift for a prime minister who has long said she is against a second referendum and staying in a customs union with the bloc.

Earlier, Labour’s finance policy chief John McDonnell cast doubt on whether Ms May’s bill could win the party’s support, saying what he had seen so far “doesn’t inspire confidence, and I don’t think that many of our members will be inspired by it”.

Brexit-supporting Conservatives were equally unconvinced.

“Her bold new offer of the WAB (Withdrawal Agreement Bill) will be a further dilution through Labour-sponsored amendments which will make her already unacceptable withdrawal agreement even more unpalatable,” Conservative MP Andrew Bridgen said.