LABOUR MPs are to snub a Commons debate on Trident organised by the SNP this week, dubbing the exercise a "meaningless stunt".

Many Labour politicians plan to boycott the event in which nationalist MPs will argue against renewing the UK's nuclear deterrent on the Clyde .

The SNP said that it would be "utterly shocking" if Labour MPs ignored the debate.

The row came as it emerged that the Ministry of Defence has estimated that spending on the project's "assessment phase" will increase by a further £261 million this year

The so-called 'main gate' decision on whether or not to press ahead with another generation of Trident has been delayed until 2016, because of disagreement between the Conservatives and the Lib Dems on how to proceed.

The Tories back a like-for-like replacement while the Libs prefer a scaled-back version.

The SNP have said that scrapping Trident would be one of their key demands to back a minority Labour government if there is a hung parliament in May's general election.

While Labour has said it wants a minimum, credible independent nuclear deterrent, it has also said that Trident should be considered as part of a full-scale defence review if the party wins May's general election.

One Labour MP said: "Labour has said that we will put Trident into the defence review. That is our position. We are not going to be taking part in the SNP's little stunt. (The debate) is going to be a damp squib".

Angus Robertson, the SNP's Westminster Leader and defence spokesman, said: "It will be utterly shocking if (Labour) avoid a debate on wasting £100 billion on new Trident nuclear weapons of mass destruction, because of their own party divisions and embarrassment.

"The way to vote against the austerity cuts and to get that £100 billion spent more productively on public services is to vote SNP in May."

Mr Robertson has also said that the general election is an opportunity to stop Trident "in its tracks" by voting SNP.

The debate is jointly organised by the SNP, the Greens and Wales' Plaid Cymru.

The motion calls for the cancellation of the renewal of the Trident weapons programme.

The SNP argue it would be fundamentally wrong to spend tens of billion of pounds of taxpayers' money on a nuclear weapons system at a time of fiscal austerity.