However, the government’s DUP allies refused to say if they would back the deal amid reports that the UK had made significant concessions, effectively keeping Northern Ireland under EU customs rules – something Theresa May previously said “no UK Prime Minister could ever agree”.
Mr Johnson will address Tory MPs tonight after briefing the Cabinet on progress in negotiations.
With Brussels’ chief negotiator Michel Barnier setting midnight last night as the deadline for a breakthrough if a deal is to be approved by EU leaders at a summit tomorrow, Downing Street kept parliamentary factions briefed on fast-moving negotiations throughout the day.
Pressure from the DUP meant the government ruled out a Northern Ireland-only solution to the problem of the Irish border in 2018, because it would see checks applied to goods crossing the Irish Sea.
DUP leader Arlene Foster held 90 minutes of talks with the Prime Minister in Downing Street last night, with the party saying in a statement that “it would be fair to indicate gaps remain and further work is required”.
Speaking to the BBC before going into Number 10, Ms Foster warned: “Everybody knows if we don’t support this deal it doesn’t reach the numbers in the House of Commons”. But the DUP leader also said that some speculation about the compromise deal was “so far off the mark, you can’t even see the mark anymore”.
Earlier Steve Baker, the chairman of the European Research Group, led a delegation of backbench Tory Brexiteers into Downing Street and emerged to tell journalists he was “optimistic that it is possible to reach a tolerable deal that I am able to vote for”. Following a meeting of the ERG last night, Mr Baker added: “I absolutely can rely on Boris Johnson to take us out of the European Union.
“The mood of the Eurosceptics meeting here tonight was that we do, we can and we must trust the Prime Minister.”
Mr Johnson is believed to have abandoned a demand that Northern Ireland’s status after Brexit be subject to approval from the devolved Stormont assembly, which EU leaders feared would grant the DUP a veto on any deal.
Reports also suggest Northern Ireland could leave the EU customs union but effectively remain under its rules. A complex system similar to the customs partnership proposed in Mrs May’s rejected Brexit deal would see EU tariffs applied to goods transiting through the province, with companies claiming rebates if the final destination in a lower-tariff jurisdiction.
Scottish Conservative pressure was also crucial in forcing Mrs May to abandon a Northern Ireland-only solution for the border, with reports suggesting former leader Ruth Davidson and ex-Scottish Secretary David Mundell threatened to quit if the Brexit deal undermined the Union.
There are also fears that special Brexit terms for Northern Ireland that keep one foot in the EU customs area and one in the UK will be seized on by the SNP as a model for a favourable deal for an independent Scotland.
But Scottish Tory MPs are understood to be more relaxed about the impact of any deal on the trading relationship between Northern Ireland and the rest of the UK, because of the political pressure to conclude Brexit and avoid a no-deal scenario.
Tomorrow’s two-day EU summit is crucial because the PM must get a new deal approved by MPs by Saturday if he is to avoid having to ask for a Brexit delay.