Jeremy Corbyn pledges to pump £30bn into South East

On Tuesday the Parliamentary Labour Party (PLP) will vote between 10am and 5pm on the issue in a secret ballot.

Pontypridd MP Mr Smith said he was ready to “look very carefully” at the reintroduction of measure, arguing that it could help create a “sense of shared ownership” of the shadow cabinet by all Labour MPs.

Supporters of the plan say that it would be an effective strategy to build unity within the parliamentary party after a summer of discord, which saw 172 Labour MPs vote that they had no confidence in Jeremy Corbyn’s leadership.

He told a PLP meeting tonight the party “can’t carry on as we are”.

The result of the leadership contest between Corbyn and Owen Smith will be announced by the end of the month.

But he said it would also put pressure on former shadow ministers to put their differences aside and return to the top team.

The Welsh MP will raise the possibility of the Labour spending at least a further decade out of power – by losing general elections in both 2020 and 2025 – with Mr Corbyn as leader, saying he had failed to make the party credible to voters.

The source quoted Betts as telling his fellow MPs: “We’ve got to find a way of working together, whoever our leader is, because we have responsibilities to all those people who’ve supported Labour in previous elections, and elections to come”.

Even if Betts’ motion is voted through, it is by no means certain to come into being.

Mr Corbyn’s spokesman said: “Jeremy supports democratisation and reform of the party rules and structures”.

She claimed she did not see how this “hurdle” would be cleared by elections to appoint shadow cabinet members.

Any final decision will have to be approved by the ruling National Executive Committee and at party conference. “Any review also needs to take account of the need to represent regions and nations”.