Rebel Labour MPs are already starting to plan how they will stand up to a victorious Jeremy Corbyn, as the party’s leadership contest enters what may be its most crucial week.

Despite calls for the party to unite behind whoever wins the contest, some of Mr Corbyn’s opponents said fellow MPs will not take a lead from him in key policy areas like Brexit or defence.

Different factions in the Parliamentary Labour Party are now said to be “building bridges” in an effort to form a more credible counter-weight to Mr Corbyn’s circle, if it is emboldened by victory in the contest.

It follows reports that MPs might try and use the Co-Operative Party, a political group affiliated with Labour, as means to oppose Mr Corbyn.

Owen Smith doesn't rule out holding Syrian peace talks with Isis

On Monday ballots will be sent out for the Labour leadership contest with much of the voting expected to take place in the next seven days.

Most of the money is on Mr Corbyn to win and MPs are beginning to think about what comes next. On record most call for a united party, but off record things become complex.

One MP told The Independent: “For years in Labour you have seen Blairites, Brownites, the soft left and so on, that would not have had anything to do with each other, but they are starting to come together.

“The different groupings have started to make peace with one another and are building bridges while Owen has been the candidate, that will leave greater strength as a group if Jeremy wins.”

The MP went on: “However it’s done, I think you are going to see a more formal alliance between those groupings in the PLP, as a much more front-footed assertive group, who refuse to give up on Labour.

“This leadership campaign is a battle, not the whole war. That is the way it will be approached now.”

Both candidates in the contest and their supporters have bemoaned the damage a disunited party is doing to Labour’s credibility in the country.

But while everyone calls for unity, they are quick to blame the other side for the lack of it, a problem unlikely to disappear according to another MP.

The Labour member said: “People are not going to suddenly change their view of Jeremy just because September the 24th occurs. People still have that view, and all the problems still exist.

“Things are going to come up where the divisions are insurmountable. People are not going to suddenly just take a lead from Emily Thornberry on Brexit.

“They are not going to suddenly just take a lead from Clive Lewis on defending the country, or the situation in Syria.”

It was suggested in reports today that there would be a drive to sign up MPs to the Co-Operative Party as a method for consolidating internal opposition against Mr Corbyn.

Many MPs do already sit jointly as Co-Op/Labour members, but the idea that the smaller party could be used as a banner for an anti-Corbyn drive has been played down.

One senior source inside the Co-Op Party said it would not be easy for Labour MPs to become affiliated without due procedure. The Co-Op’s own executive committee favours neutrality when it comes to the Labour leadership.

Another Labour MP cast doubt on whether different parts of the PLP could come together to oppose Mr Corbyn.

The person said: “It’s really not clear cut what’s going to happen. There are still tensions between different groups.

“A lot will depend on how Jeremy would act after a victory. There is talk of him trying to push out [Labour chief whip] Rosie Winterton.