Black Country MP Tom Watson has resigned from his post as Labour’s campaign co-ordinator after finding himself at the heart of a row over claims a trade union was trying to fix the selection of candidates.

Mr Watson (Lab West Bromwich East) came under fire over claims the union tried to install his Parliamentary aide Karie Murphy as the candidate in Falkirk, Scotland.

Labour was forced to suspend the selection process after it was alleged up to 150 Unite members signed up to the local party, with their membership fees paid with a single cheque from the union, as part of a campaign to decide the outcome.

Unite’s general secretary, Len McCluskey, is a former flatmate of Mr Watson.

And it has now emerged that Unite has been backing potential candidates in Labour’s internal selection battles in seven West Midland seats, as part of a campaign to push the party to the left.

Leaked documents show the union backed Steph Peacock, who was selected as Labour’s candidate in Halesowen and Rowley Regis, Mike O’Brien, who was selected in North Warwickshire, and Rob Marris, who was selected in Wolverhampton South West.

The party is also backing three potential candidates in seats where the selection process is still underway - Mirian o’Reilly in Nuneaton, Pete Lowe in Stourbridge and Natasha Millward in Dudley South.

All the seats are marginals which the Conservatives hold with relatively small majorities.

Unite also backed a potential candidate in Birmingham Yardley, which is held by Liberal Democrat John Hemming, but failed to get them selected.

Mr Watson has now quit from his post as Labour Deputy Chairman and campaign co-ordinator, which gave him a seat on the party’s Shadow Cabinet.

And in his resignation letter, published on his blog, he revealed that he actually offered to go on Tuesday - but Labour leader Ed Miliand asked him to stay.

The MP said he was resigning because of “spurious suppositions being written” about his involvement with the Falkirk selection.

But he said he also wanted to be free to pursue his interests as a backbencher, saying: “I wish to use the backbenches to speak out in areas of personal interest: open government and the surveillance state, the digital economy, drones and the future of conflict, the child abuse inquiries, the aftermath of the Murdoch scandal and grass roots responses to austerity.”

It is the third time Mr Watson has resigned from a front bench position.

He quit his job as a Defence Minister in Tony Blair’s government in 2006 as part of a campaign to pressure Mr Blair into naming the date of his resignation. He also quit as a Minister in Gordon Brown’s government in 2009.

Conservative leader David Cameron, the Prime Minister, raised Unite’s role repeatedly during Questions to the Prime Minister on Wednesday.

And it has emerged Mr Miliband was preparing to answer criticism about Tom Watson, if the Prime Minister had bought him up.

Mr Miliband’s briefing notes - which have been published after they were left in a House of Commons lavatory by a Labour MP - show that he was ready to tell David Cameron: “I’d far rather have Tom Watson working for me, who led the campaign on the phone hacking scandal, than have brought Andy Coulson into the heart of Downing Street.”

Jim Murphy, the Shadow Defence Secretary, has condemned the union’s behaviour in Falkirk, saying: “While trade unions are an important part of a society and our politics, there seems to be one trade union in particular that has well and truly overstepped the mark. It’s clear that Unite don’t run the Labour party – Ed Miliband does.”

Meanwhile, details of the union’s involvement in supporting potential Labour candidates in 41 seats across the country were revealed in a report by Steve Hart, the union’s political director, presented to Unite’s executive council on May 11.

Mr Hart admits that he is keeping details of the union’s attempts to influence candidate selection private, saying: “I do not intend to give a detailed written report. Previous reports to the Executive Council have found their way on to web sites or been quoted in the press, so of neccesity some of this will be verbal.”

But he continues: “The work of the political department and the union regionally in candidate selections is a little bit like a swan - all that can be seen is indication of support here or there, while below the water activity is furious!”

The document makes it clear that Unite is attempting to marginalise the “Labour right” and what it calls “New Labour continuity”, and instead it is attempting to push the party into accepting a “radical alternative”.

There is particular criticism of the party’s stance on welfare, where  Birmingham MP Liam Byrne (Lab Hodge Hill), the Shadow Work and Pensions Secretary, is in charge of policy.

Some members of the Shadow Cabinet have urged Labour leader Ed Miliband to confront Unite, after David Cameron made the selection row the theme of Prime Minister’s Questions this week.

Tom Watson after winning the West Bromwich East seat at the 2010 General Election
Tom Watson after winning the West Bromwich East seat at the 2010 General Election
 

• Tom Watson's resignation letter to Ed Miliband

Dear Ed,

I said that I’d stay with you as general election co-ordinator within the Shadow Cabinet as long as I was useful. I think it would be a good idea for you, and me, if I stood down from the role now.

As you know, I offered my resignation on Tuesday and you asked me to reconsider. I’ve thought about it and still feel it is better for you and the future unity of the party that I go now. There are some who have not forgiven me for resigning in 2006. I fully accept the consequences of that decision and genuinely hope my departure allows the party to move on.

Yet it’s not the unattributed shadow cabinet briefings around the mess in Falkirk that has convinced me that the arrangement has run its course (though they don’t help). I believe that the report should be published – in full – and the whole truth told as soon as possible so that the record can be made clear. I’ve still not seen the report but believe there are an awful lot of spurious suppositions being written.

I wish to use the backbenches to speak out in areas of personal interest: open government and the surveillance state, the digital economy, drones and the future of conflict, the child abuse inquiries, the aftermath of the Murdoch scandal and grass roots responses to austerity.

Having resigned a couple of times before, I know how puckish lobby hacks might choose to misconstrue the departure.

So to make it harder for them let me say this: I’m proud of your Buddha-like qualities of patience, deep thought, compassion and resolve. I remain your loyal servant. I’ll always be on hand to help you if you need me. I just don’t think you need me in the Shadow Cabinet any more. After nearly thirty years of this, I feel like I’ve seen the merry-go-round turn too many times. Whereas the Shadow Cabinet’s for people who still want to get dizzy.

You have it in you to be an outstanding Labour Prime Minister. The road ahead is always rocky but I will be with you all of the way, cheering you on from the backbenches. You’re my friend and leader, and I’m going to do all I can to make sure you win in 2015.

Here’s my parting thought:

John Humphrys asked me why you were not at Glastonbury this weekend. I said Labour leaders can’t be seen standing in muddy fields listening to bands.

And then I thought how terribly sad that this is true. So: be that great Labour leader that you can be, but try to have a real life too. And if you want to see an awesome band, I recommend Drenge.

Yours sincerely,

Tom Watson

Member of Parliament for West Bromwich East