Embattled Liz Truss will treat a vote in the Commons tonight seeking to ban fracking as a "confidence motion" in her Government.
The severely weakened Prime Minister, who is facing calls to resign, has ordered Tory MPs to vote against the motion with a three-line whip.
The move comes as Labour launches an audacious bid to force a ban on fracking by giving the party powers to seize control of the parliamentary timetable next month.
If passed, the Opposition day debate motion would guarantee Commons time for a Bill banning fracking once and for all.
The vote will be held at 7pm, but on Wednesday morning government whips emailed Tory backbenchers telling them it will be treated as a "motion of confidence".
Deputy Chief Whip Craig Whittaker told them it will be a "100% hard" three-line whip, saying: "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"We are voting NO and I reiterate, this is a hard 3 line whip with all slips withdrawn."
The Government amendment supporting giving fracking the go-ahead in areas where local consent is deemed to have been given was also made a three-line whip.
"I know this is difficult for some colleagues, but we simply cannot allow this," Mr Whittaker wrote.
Thangam Debbonaire, the Shadow Leader of the Commons, 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.
"The Tories must urgently confirm this is the case".
Tory MP Steve Double, who represents the Cornwall constituency of St Austell and Newquay, argued Labour has "overplayed their hand on this occasion".
"Whatever your views for or against fracking, Conservative MPs shouldn't be voting to allow the Labour Party to take over the order paper," he told BBC News.
