Liz Truss was at risk of a significant Commons rebellion over fracking on Wednesday after a series of senior MPs, including the head of her net zero review, announced they would vote against the government on a Labour motion on the controversial policy. This was despite Conservative whips billing the vote, on a Labour opposition day motion seeking to give parliamentary time for a bill that would outlaw shale gas extraction, as a confidence motion – meaning rebels would lose the Tory whip. Chris Skidmore, a former minister and leading voice of green Tories, who Truss appointed in September to examine the government’s route towards net zero emissions by 2050, said he was willing to accept this. “As the former energy minister who signed net zero into law, for the sake of our environment and climate I cannot personally vote tonight to support fracking and undermine the pledges I made at the 2019 general election,” Skidmore tweeted, adding: “I am prepared to face the consequences of my decision.” Tracey Crouch, another former minister, retweeted Skidmore’s message with the added word: “Ditto.” Angela Richardson, an MP from the 2019 intake, then did the same. The growing rebellion added to a nightmarish day for the prime minister in which she attempted to claw back some authority at prime minister’s questions before losing her home secretary, Suella Braverman, who resigned with a vicious swipe at Truss in her departing letter. Earlier, Jacob Rees-Mogg, the business and energy secretary, sought to quell Conservative MPs’ fury at being told to vote down the motion by setting up a public consultation on the practice. Ed Miliband, the shadow climate and net zero secretary, called on others to join Skidmore. He said: “The government’s defence of fracking is collapsing. But the way to put an end to this once and for all is to vote for Labour’s motion to bring in a bill to ban fracking.” Rees-Mogg, in an attempt to head off consternation in the party’s ranks, said the issue of how communities should be able to approve or reject fracking in their area would be opened up to a public consultation. He has tabled an amendment to the motion, which will be voted on at about 7pm on Wednesday. However, a series of Tory MPs used the debate to press Rees-Mogg over the practicalities of local consent. Greg Knight urged him to remove the ability of planning inspectors to overturn councils’ decision on fracking, so these were considered the “expression of local consent”. Seven cabinet ministers are among those who have spoken out against fracking, including the chancellor, Jeremy Hunt, who said in June that it would create “enormous disruption and environmental damage for little if any economic benefit”. The Conservatives’ 2019 manifesto promised to maintain a moratorium on fracking unless there was new evidence on the risk of earthquakes from the practice. But Truss’s government changed this last month, to the anger of campaigners and a number of Tory MPs. Opening the debate, Miliband said the government was pursuing a “frack me or sack me strategy”, saying fracking was “one of the most unpopular causes in the country”. He added: “In normal times such an idiotic idea would have been dismissed out of hand but these are not normal times. But I say to the house and I say to members opposite, they all know that the prime minister will be gone in a matter of weeks, if not days, if not hours.” In a message to all MPs on Wednesday morning, the Tory deputy chief whip, Craig Whittaker, said: “The second debate is the main event today and it is a 100% hard three-line whip. This is not a motion on fracking. This is a confidence motion in the government. “We cannot, under any circumstances, let the Labour party take control of the order paper and put through their own legislation and whatever other bits of legislation they desire. We are voting NO and I reiterate, this is a hard two-line whip … I know this is difficult for some colleagues, but we simply cannot allow this.” Labour called on ministers to “urgently clarify” the status of the vote. Thangam Debbonaire, the shadow Commons leader, said: “The consequence of making this a confidence vote is that if the government loses the motion on fracking, the prime minister will resign and the government will fall.” Labour sources said Tory whips had walked into a trap set for them, and that although they did not expect to win the vote, Labour had online adverts ready to go, targeting every Tory MP who backed fracking.