Rebel ex-Conservative MPs have dismissed the idea that Boris Johnson could get around a backbench bill forcing him to seek an extension to Brexit, as they warned that more cabinet ministers could follow Amber Rudd in quitting.

Johnson was heading to Dublin on Monday to meet the Irish prime minister, Leo Varadkar, having suffered yet another political blow with the resignation of Rudd, the work and pensions secretary, over the weekend.

With the Dublin trip seen as key in persuading other worried ministers that Johnson is serious about trying to negotiate a new Brexit deal, Johnson will face a sceptical reception in Ireland, with the Irish government stressing it has yet to see even the basics of a supposed replacement for the backstop border insurance policy.

Rory Stewart, the former international development secretary who was among 21 Tory MPs ejected from the party for backing plans to push through the bill mandating a Brexit delay, said he believed there were other ministers considering their positions.

“Yes, I think there are,” he told BBC Radio 4’s Today programme. “Because everybody who was in the cabinet with me and Amber, under Theresa May’s government, was very aware of the dangers of a no-deal Brexit. And remember, very, very recently – barely seven weeks ago – the formal policy of the cabinet was to avoid a no-deal Brexit.”

Q&A Who were the 21 rebel Tories? Show Hide Here is the list of the 21 Conservative MPs who voted with the opposition and against the government to seize control of the parliamentary timetable in order to pave the way for a bill to block a no-deal Brexit. They were then thrown out of the party by prime minister Boris Johnson. Guto Bebb, Aberconwy Richard Benyon, Newbury Steve Brine, Winchester Alistair Burt, North East Bedfordshire Greg Clark, Tunbridge Wells Kenneth Clarke, Rushcliffe David Gauke, South West Hertfordshire Justine Greening, Putney Dominic Grieve, Beaconsfield Sam Gyimah, East Surrey Philip Hammond, Runnymede and Weybridge Stephen Hammond, Wimbledon Richard Harrington, Watford Margot James, Stourbridge Sir Oliver Letwin, West Dorset Anne Milton, Guildford Caroline Nokes, Romsey and Southampton North Antoinette Sandbach, Eddisbury Sir Nicholas Soames, Mid Sussex Rory Stewart, Penrith and The Border Edward Vaizey, Wantage



Later on Monday, the rebel bill that led to Stewart and others losing the Tory whip is expected to receive royal assent. It will mandate Johnson to seek a Brexit delay till 31 January if, by the middle of next month, he has not passed a departure deal or got MPs’ consent for no deal.

Stewart dismissed reported ideas that Johnson – who has pledged to never seek a delay – could seek to get round the law, for example by adding a second letter to the mandated approach to the EU over an extension spelling out that he does not actually want this.

“I remain very, very confident we can stop no deal. Because in the end parliament is sovereign, and we are making a positive case for a moderate, pragmatic solution to the problem,” he said.

David Gauke, the former justice secretary and another key rebel, said a separate letter would be pointless given the EU would know it was not the will of parliament. “The European Union are perfectly capable of following our news stories,” he told BBC1’s Breakfast programme.

Of a parallel letter, Gauke said: “It carries no weight. Statute will say that the position is that the prime minister is writing to the European Union seeking an extension. Now, of course, the European Union can refuse that extension. I personally think that they wouldn’t want to be blamed for a no-deal Brexit and they will agree to an extension.”

While saying he was “very confident” that Johnson would ultimately comply with the new law, he condemned anonymous briefings that No 10 could decide to simply ignore it, calling this “damaging to our reputation”.

Also speaking on Monday, the former supreme court justice Lord Sumption said it would not be legal for Johnson to apply for a Brexit extension while simultaneously trying to get the EU to reject it.

“No, of course it wouldn’t,” he told Today. “The bill, or act as it’s about to become, says that he’s got to apply for an extension. Not only has he got to send the letter, he’s got to apply for an extension. To send the letter and then try to neutralise it seems to me, plainly, a breach of the act. What you’ve got to realise is the courts are not very fond of loopholes.”

When he returns from Dublin later on Monday, Johnson is expected to make a second attempt to trigger a general election on 15 October by asking MPs to support a motion tabled under the Fixed-term Parliaments Act.

But he is almost certain to be rebuffed for a second time, after opposition leaders agreed on Friday to reject a snap poll until a no-deal Brexit has been definitively avoided.

Speaking before the Dublin trip the Irish finance minister, Paschal Donohoe, told Today he remained unclear about much-touted UK government plans for alternative arrangements to replace the backstop, the guarantee against a hard Irish border, which Johnson has vowed to scrap.

“What I would say to those who are putting those ideas forward is we are yet to see examples of how they would work not only on our island but anywhere else in the world,” he said.

“To be in a situation where we would have one part of our island inside the single market and the other outside the single market is a very, very testing challenge for alternative arrangements.”