Theresa May will face Tory MPs who are increasingly concerned about her Brexit plans in Westminster on Wednesday.
The showdown comes as the number of Tory MPs publicly committed to oppose her Chequers blueprint for leaving the European Union reached 50.
The Prime Minister will meet critics at the backbench 1922 Committee in Parliament just days after one anonymous opponent suggested she should “bring her own noose” to the gathering.
The meeting follows fresh revelations about the Government’s plans for a no-deal Brexit, with alternative measures to secure supplies of food and medicines from the continent being investigated in case of chaos on the English Channel crossing.
And in developments which will cause further unease among Tory Brexiteers, leaked Cabinet papers obtained by The Times indicated the transition period during which the UK will remain tied to Brussels could turn into a “long-running” arrangement lasting years.
The option of extending the transition period has been put forward as a way of resolving the impasse over the Irish frontier by giving extra time to find a mechanism to avoid a hard border.
The transition period is due to expire at the end of 2020 and Mrs May has insisted that if an extension is necessary it should only last a few months.
But the leaked documents conceded that the plan “could, in theory, lead to a long-running IP (implementation period)”.
The arrangement could last for many years on a “rolling” basis with an annual decision on whether to extend the period.
Responding to the leak, a Downing Street spokesman said: “This is nothing more than a partial reflection of advice to ministers, and not of decisions taken – the Prime Minister made her position absolutely clear in the House of Commons on Monday.
“As the PM said then, we do not believe any extension to the implementation period will be necessary, and in any event we would have to be out of it well before the end of the Parliament.
“We would not accept a position in which the UK, having negotiated in good faith an agreement which prevents a hard border in Northern Ireland, nonetheless finds itself indefinitely locked into an alternative, inferior arrangement against our will.”
Confirmation of Mrs May’s attendance at the 1922 Committee comes amid speculation that the number of Conservative MPs submitting letters calling for her removal is approaching the 48 needed to trigger a no confidence vote in her leadership.
The scale of opposition her Brexit plans face was made clear as the Stand Up 4 Brexit campaign, which has received high-profile support from former foreign secretary Boris Johnson, said Sir Edward Leigh had become its 50th backer.
Meanwhile, the Government’s contingency preparations for a no-deal Brexit were mocked following reports that ships may have to be chartered by Whitehall to ensure vital supplies reach the UK.
The Financial Times said Transport Secretary Chris Grayling had discussed the possibility of hiring entire vessels, or securing space in ships, to bring food, medicines and other supplies in through alternative ports.
A Department for Transport spokesman said: “We remain confident of reaching an agreement with the EU, but it is only sensible for government and industry to prepare for a range of scenarios.
“We are continuing to work closely with partners on contingency plans to ensure that trade can continue to move as freely as possible between the UK and Europe.”
But pro-EU Labour MP David Lammy said: “Brexit has become like a declaration of war on ourselves.
“Emergency ships will be chartered for food and medicine if we leave the EU with no deal.
“But at least when we’re using ration books and running out of drugs, we’ll have taken back control.”