Culture Secretary Tessa Jowell has refused to drop an all-or-nothing ultimatum to MPs over supercasinos despite a late Tory decision to vote alongside Labour rebels.
Plans to build Britain's first Las Vegas-style gambling venue in Manchester could be put in jeopardy if the Government cannot persuade critics by Wednesday's Commons vote.
More than 100 MPs - including 83 from Labour - have signed a parliamentary motion expressing "surprise and regret" at the selection of Manchester.
Critics warn the city's relatively high levels of unemployment and income support mean there are too many vulnerable people who would have easy access to gambling.
And they want the decision to be reconsidered by a panel of MPs and peers, accusing Ms Jowell of failing to consult widely before endorsing the Casino Advisory Panel's conclusions.
Blackpool and London had been the favourites to win the competition to host the supercasino.
David Cameron's party only decided on Friday to vote against the package after, a spokesman said, being persuaded by a critical report into the process by a Lords committee.
They called on Ms Jowell to offer MPs two separate votes on the Manchester decision and the location of 16 smaller regional casinos - which they back.
But the Department of Culture, Media and Sport insisted there was "absolutely no question" of such a compromise being made.
