Theresa May is setting out the details of a series of compromises designed to try and win the support of Labour MPs for her Brexit plan.
The cabinet earlier agreed the idea of a temporary customs relationship until the next general election, and measures on the environment and workers’ rights.
These will be included in the Withdrawal Agreement Bill, to be put to a vote in the Commons in early June.
The SNP and some Tory Brexiteers have already said they will vote against.
The PM briefed MPs and ministers on the contents of the speech – entitled “A new Brexit deal – seeking common ground in Parliament” – beforehand.
The Withdrawal Agreement Bill is legislation required to bring the withdrawal agreement negotiated with the EU into British law.
MPs have rejected the withdrawal agreement three times, and talks with Labour on finding a compromise deal acceptable to their MPs broke down last week.
Downing Street said there was a “shared determination” in cabinet to find a way of passing the legislation although it conceded “strong opinions” had been aired on how best to do this.
At the meeting, Mrs May told her ministers: “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.”
No 10 said the bill, when it was published, would contain “some significant new aspects”.
International Development Secretary Rory Stewart suggested on Sunday that the government and Labour were “half an inch apart” on key issues and “sensible” Labour MPs could be won round.
But shadow foreign secretary Emily Thornberry said she believed her colleagues would vote against the Withdrawal Agreement Bill as she had heard there was “no radical difference” in what was being offered.
For Theresa May getting her cabinet behind her plan for another push towards a Brexit deal was the easy bit.
Ministers agreed legislation to deliver Brexit should be the vehicle for compromises to bring enough Labour MPs on board to counteract the still strong rebellion by those on her own side.
The plan supersedes the idea of so-called indicative votes in the Commons on Brexit options.
The problem is that opposition on the Conservative side has probably hardened, not softened, since her last failed attempt.
The hope in Downing Street is that those wanting another referendum or a form of Brexit that keeps us closer to the EU may back this bill and try and get their way during later detailed debate.
The emphasis now is on hope and perhaps not very much of it.