It would be “staggeringly hypocritical” for the government to sack Conservative MPs who rebel over its Brexit plans, former chancellor Philip Hammond says.
It comes after the Sun reported No 10 would stop any Tory MP who votes to block a no-deal Brexit from standing for the party in a general election.
Government sources haven’t denied this.
But Mr Hammond said eight current cabinet members had themselves defied the party whip this year by voting against Theresa May’s Brexit deal.
On Wednesday, Prime Minister Boris Johnson announced that Parliament would be suspended, or prorogued, just days after MPs return to work in September, prompting an angry backlash from MPs and opponents of a no-deal Brexit.
The prime minister said the move would enable the government to bring forwards new legislation.
But Labour leader Jeremy Corbyn accused Mr Johnson of a “smash and grab on our democracy” in order to force through no deal by leaving MPs too little time to pass laws in Parliament aimed at preventing such an outcome.
At present, the default position in law is that the UK leaves the EU on 31 October, with or without a deal.
Some MPs who oppose a no-deal Brexit – including Conservatives – are planning to take action in Parliament next week.
Mr Corbyn has said opposition MPs have agreed to first try to avoid no deal using legislation, while using a vote of no confidence to bring down the government remained an option.
According to the Sun, Mr Johnson plans to sack any Tory MPs who back either of these moves.
In response to the reports, Mr Hammond tweeted that he wanted to honour the party’s 2017 manifesto promise for a “smooth and orderly” exit and a “deep and special partnership” with the EU and “not an undemocratic No Deal”.
Conservative MP Sam Gyimah tweeted that the possibility of every MP who votes against “no-deal chaos” being purged showed the direction the party had gone in a very short space of time, adding that it was not “real Conservatism”.
And Conservative backbencher Antoinette Sandbach has said she will “always put [her constituents] interests above my career prospects” and her party.
Government sources told the BBC that Mr Johnson wanted all MPs to “recognise their duty” and “give him their support” to get the UK out of the EU by 31 October.
A government spokesperson said: “All options for party management are under consideration, but first and foremost the PM hopes MPs will deliver on the referendum result and back him on Parliament.”
By Jessica Parker, political correspondent
Whether Boris Johnson’s government would really go so far as to throw rebellious MPs out of the party isn’t yet certain.
But the fact that today’s reports aren’t being denied is yet another indication that Downing Street is, it appears, doing its best to dissuade wavering Conservatives from supporting legislation designed to block a no-deal Brexit.
Mr Johnson believes that taking that outcome off the table will weaken his hand in trying to get a new agreement.
However, some MPs take the view that this administration is being deliberately provocative, perhaps with the aim of being able to create that “People versus parliament” narrative in the event of a general election.
Mr Hammond’s intervention came after his successor, Sajid Javid, backed Mr Johnson’s decision to suspend Parliament.
Despite insisting during the Tory leadership campaign that he thought proroguing Parliament was a bad idea, Mr Javid has now defended the plan.
He told BBC Radio 4’s Today programme: “It is quite usual this time of year, Parliament goes into what’s called a conference recess and it doesn’t usually sit for some time in September and early October.
“It’s right because we are focusing on the people’s priorities.”
Thousands of people took to the streets across the UK to protest the suspension on Saturday.
Demonstrations were held in central London, near Downing Street, and in other locations across the UK, including Manchester, Leeds, York and Belfast.