Analysis By Nick Assinder Political Correspondent, BBC News website

The Tories do not necessarily expect victory in their bid to defeat the government's 24 hour drinking proposals - but that is not the point.

Theresa May thinks vote is a winner

By forcing this issue back into the Commons, the opposition is actually engaged in a game of "name and shame".

Tory spokesman Theresa May - who discovered a little-used piece of parliamentary procedure to spark the vote - believes the public is not in favour of extended licensing laws.

So it is only right that MPs should be made to show where they stand on the issue so they can be held responsible when, as she expects, it all goes horribly wrong with an increase in drink-related incidents.

And if that leads to any sort of backbench Labour rebellion it will be a bonus for the opposition at a time when it believes Tony Blair is still in shock after the defeat of his anti-terror laws.

The fact that the vote is being held on an Opposition debate day - when ministers are generally freed from the need to be around to vote at Westminster - means there is an outside chance the legislation could actually be blocked.

Drink more

Either way, to use Mrs May's own words, this is a "no brainer". There is, she believes, no way the Opposition can lose this one.

She points to the apparent irony of the fact that, just a week before the new laws are supposed to come into effect, the government is also launching its toughest, and most controversial anti-drinking campaign ever.

"If you give people longer to drink, they will drink more," she argues.

And that will inevitably add to the widely accepted problem of binge drinking in Britain which the new campaign is designed to combat.

Ministers, on the other hand, believe the public is on their side and that it would be unjust to punish the majority of sensible "grown up" drinkers because of the activities of a few immature trouble makers.

Grown ups

The new laws allow pubs and clubs to stay open for longer - even 24 hours if they so chose - but they also give the police the toughest powers yet to combat binge drinking.

According to the minister responsible, James Purnell, it is all part of a package designed to combat drunken behaviour by stopping eleven o'clock "speed drinking" and widening the type of places where late drinking is allowed, while also refusing to tolerate drunken behaviour.

"The important thing is to give the police the powers they need and then treat the rest of us like grown-ups," he said.

To stop the changes now would cause chaos and probably anger in the run-up to Christmas.

The government is expected to win the vote, but what this row displays is the Tories' determination to keep the government on the back foot at every possible opportunity.