Update 16.40pm: British Prime Minister Theresa May said her Withdrawal Agreement Bill will include a vote by MPs on whether to hold a second referendum.
The Withdrawal Agreement Bill will go to the Commons in early June, with defeat likely to hasten Mrs May’s departure as the UK's Prime Minister.
"I recognise the genuine and sincere strength of feeling across the House on this important issue.
"The Government will therefore include in the Withdrawal Agreement Bill at introduction a requirement to vote on whether to hold a second referendum and this must take place before the Withdrawal Agreement can be ratified."
Mrs May 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".
She said: "If MPs vote against the second reading of this Bill they are voting to stop Brexit.
"If they do so the consequences could hardly be greater - reject this deal and leaving the EU with a negotiated deal any time soon will be dead in the water and what would we do then?
"... If not no-deal then it would have to be a general election or a second referendum that could lead to revocation and no Brexit at all."
As she ended the speech, Mrs May said: “This is a huge opportunity for the United Kingdom.
“Out of the EU. Out of ever-closer union. Free to do things differently. And doing so in a way that protects jobs, protects our security, maintains a close relationship with our friends and works for the whole United Kingdom.
“It is practical. It is responsible. It is deliverable. And right now, it is slipping away from us. We risk losing a great opportunity.”
Update 4.20pm: British Prime Minister Theresa May has said there is "one last chance" to help MPs deliver the result of the 2016 referendum, as she offered a "new Brexit deal".
Mrs May is outlining her latest plan to push her Withdrawal Agreement through Britain's Parliament on the fourth attempt and see the UK achieve Brexit.
The speech follows a UK Cabinet meeting where two hours was spent discussing the Brexit plan, with Mrs May’s spokesman acknowledging there were “strong opinions” around the table but also a “determination” to get a deal through Parliament.
The Withdrawal Agreement Bill will go to the Commons in early June, with defeat likely to hasten Mrs May’s departure from Number 10.
Mrs May began her speech just after 4pm, recounting her efforts over the past two years to achieve Brexit.
Mrs May said the new Brexit deal will seek to conclude alternative arrangements for the Irish backstop by December 2020.
She said: "Although it's not possible for (alternative arrangements) to replace the backstop in the Withdrawal Agreement, we can start the work now to ensure they are a viable alternative.
Mrs May said: "The new Brexit deal will set out in law that the House of Commons would approve the UK's objectives for the negotiations on our future relations with the EU.
"And they will approve the treaties governing that relationship before the Government signs them."
Mrs May said her new Brexit deal had "listened to Unionist concerns" about the backstop.
"So the new Brexit deal goes further," she said. "It will commit that should the backstop come into force the Government will commit to ensure that Great Britain will stay aligned with Northern Ireland.
"We will prohibit the proposal that a future government could split Northern Ireland off from the UK's customs territory."
- Press Association
Update 1.53pm: Theresa May will set out details of her new plan to get a Brexit deal through Britain's Parliament after another difficult Cabinet meeting.
The “new deal” is an attempt by the British Prime Minister to win over critics across the Commons who have rejected her three previous attempts to get an agreement through.
The Withdrawal Agreement Bill (WAB) will go to the Commons in early June, with defeat likely to hasten her departure from Number 10.
Mrs May told the UK Cabinet: “The Withdrawal Agreement Bill is the vehicle which gets the UK out of the EU and it is vital to find a way to get it over the line.”
During the two hours spent discussing the Brexit plan, Mrs May’s spokesman acknowledged there were “strong opinions” around the Cabinet table but also a “determination” to get a deal through Parliament.
“The discussions included alternative arrangements, workers’ rights, environmental protections and further assurances on protecting the integrity of the UK in the unlikely event that the backstop is required,” the spokesman said.
The talks also covered the “whole range of topics” related to the Withdrawal Agreement Bill, including customs arrangements and calls for a second referendum.
The meeting was “characterised by a shared determination to find a way of passing the WAB so that the UK can leave the EU with a deal”, the spokesman said.
But “Brexit is a topic which does carry strong opinions” and “they are very often reflected around the Cabinet table”.
Downing Street said the package contained “significant new aspects” after MPs resoundingly defeated previous versions of the deal three times.
Ministers also considered the ongoing preparation for a no-deal Brexit if an agreement has not been ratified by October 31.
In a sign of the divisions within the party, Chancellor Philip Hammond will use a major speech tonight to deliver a rebuke to would-be leaders considering a no-deal Brexit.
The Chancellor will claim supporters of leaving the bloc without an exit agreement are trying to “hijack” the result of the referendum.
But Commons leader Andrea Leadsom, who has said she could stand in the contest to replace Mrs May, insisted the UK had to be prepared to walk away without a Brexit deal.
Despite the collapse of cross-party talks with Labour, the WAB contains a series of commitments on workers’ rights and environmental protections designed to appeal to opposition MPs.
It also contains commitments to look at alternative arrangements to prevent the need for the controversial backstop aimed at keeping a soft border with Ireland, an olive branch for Tory Brexiteers and the DUP.
Mrs Leadsom, one of the Cabinet’s leading Brexiteers, said she would support the Bill, but warned that could change if its provisions were watered down.
“I continue to support the Prime Minister to get her Withdrawal Agreement Bill through,” she told BBC Radio 4’s Today. “It is leaving the European Union and so long as it continues to be leaving the European Union, I continue to support it.
“What I do think is that for any negotiation to succeed, you have to be prepared to walk away.”
But shadow foreign secretary Emily Thornberry dismissed the idea of Labour supporting it, claiming the Bill was a “piece of political theatre” for Mrs May to have one last shot at getting her deal through.
“It’s almost like she is setting up her own political version of the last rites,” she told Today. “She cannot realistically expect to see this get through without fundamental changes and we are not going to see fundamental changes, from everything I hear.”
Defeat for the WAB will accelerate Mrs May’s departure from Downing Street, with the Prime Minister due to set out the timetable for the contest to replace her after the vote.
In a warning to leadership contenders, the Chancellor will use a speech to the CBI’s annual dinner in London on Tuesday to highlight the risk of “right-wing populism”.
He will say that if the Brexit issue is not resolved in the next few weeks, there is a “real risk” of a new prime minister moving towards a “damaging” no-deal exit policy for “ideological” reasons.
In what is likely to be seen as a sharp dig at prominent Tory Brexiteers like ex-foreign secretary Boris Johnson, Mr Hammond will say “all the preparation in the world” will not avoid the consequences of no deal.
- Press Association