DETAILS of the "personal issues" that forced shadow chancellor Alan Johnson to quit were starting to emerge today amid allegations that the politician's bodyguard had an affair with his wife.
Mr Johnson's close protection officer when he was home secretary, Paul Rice, is facing an internal Scotland Yard inquiry over his alleged behaviour.
A decision is expected to be taken shortly on whether the constable will be suspended or relieved of duty while the probe takes place.
Mr Johnson, the Hull West and Hessle MP, dramatically resigned from the Labour front bench last night, saying he was finding it "difficult to cope" with "personal issues in my private life".
Responding to reports that Laura Johnson had an affair with Mr Rice, a Yard spokesman said: "Certain matters regarding a Metropolitan Police Service Pc were referred to the directorate of professional standards.
"We are not in a position to discuss further at this time. No officer is suspended or relieved of duties at this time."
Mr Rice is said to be deployed protecting current Home Secretary Theresa May.
Mr Johnson's spokesman has refused to comment on the claims, while the Home Office said it did not comment on personal security matters.
Shadow minister Tessa Jowell told BBC2's Newsnight she did not know why Mr Johnson had resigned, but added: "He's clearly very distressed. It's clearly a very, very difficult time for him."
In his statement, Mr Johnson said only that it was "to do with my family".
"I have found it difficult to cope with these personal issues in my private life whilst carrying out an important frontbench role," he added.
Mr Johnson has been married to his second wife Laura for almost 20 years and the couple have a 10-year-old son.
His resignation left Ed Miliband facing his biggest test since being elected Labour leader, forcing him to reshuffle his shadow cabinet less than four months into the job.
He installed Ed Balls as shadow chancellor after overlooking him last October.
Amid suggestions that Mr Balls may drag Labour to the left, Mr Miliband stressed that there would be no change in economic policy.
Mr Balls, a fierce ally of former prime minister Gordon Brown, has questioned Labour's deficit reduction plans in the past, suggesting they should be less aggressive.
Mr Miliband said: "Ed brings great expertise to this role and I look forward to working with him on the direction Alan and I have set out.
"Economic policy is unchanged. Actually Ed and I have similar views."
Labour's deputy leader Harriet Harman told BBC Breakfast: "I can't say anything about that. If there's any comment to be made about a police officer, I think that comment will have to come from the police. I do want to say that I think Alan Johnson's resignation is a real loss to frontline British politics.
"He's somebody who, even though he achieved the highest office in politics, he really never lost touch with his roots. He's a loss to British politics as well as to us in the Labour Party.
"Ed Miliband, the Labour leader, has reshuffled the team and we have got a very strong team to take forward our job in opposition."
Referring to the relationship between Mr Miliband and Ed Balls, she said: "I think they'll have a very dynamic and productive relationship, with Ed Balls being, I'm sure, an exceptional shadow chancellor under Ed Miliband's leadership. He's got a great deal of experience on economic issues."
But the Tories and Liberal Democrats said Mr Balls' appointment marked a return to strength for Gordon Brown's old guard.
Conservative Party deputy chairman Michael Fallon said: "It beggars belief that Ed Balls has been appointed as shadow chancellor of the Exchequer.
"The man who is responsible for Britain's economic mess has returned. The Labour Party has learnt nothing and is now led entirely by Gordon Brown's old team."
Stephen Williams, co-chair of the Lib Dem Parliamentary Treasury Committee, accused Mr Balls of being a "deficit enthusiast".
Mr Johnson's abilities as shadow chancellor had been repeatedly called into doubt by opponents - something he helped encourage by saying he needed to buy a primer on economics.
But Mr Miliband denied that Mr Johnson had been the wrong choice for shadow chancellor in the first place.
"No, Alan Johnson was the right person for the job. He's had to stand down for personal reasons, nothing to do with the job," he said.
Labour sources said Mr Johnson approached the leader on Monday to tell him that he wanted to stand down and explained why he felt he could not continue as shadow chancellor.
Mr Miliband spent the past few days trying to persuade Mr Johnson to stay on.
Mr Balls said he planned to "carry on" the work started by Mr Johnson.
"Ed and Alan in the last few months have set out the direction that is going to continue," he said.
"Alan has stood down for personal reasons - I think everybody knows that is absolutely genuinely what is happening here.
"It is tough and he is a great loss, but I am going to carry on the work he has done."
A Labour reshuffle will see Yvette Cooper, Mr Balls' wife, take over from him as shadow home secretary.
Douglas Alexander becomes shadow foreign secretary, Liam Byrne will be shadow work and pensions secretary and Ms Jowell takes over as shadow Cabinet Office minister.
Prime Minister David Cameron was asked for his views on Mr Johnson's resignation during a visit to RAF Brize Norton.
Mr Cameron told reporters: "Obviously I am very sorry for Alan because he has given a huge amount of service in public life - on the front line in public life.
"He's one of the more cheerful and optimistic characters in politics.
"I am sure he will go on doing a good job for his constituents and being a Member of Parliament and I hope that he is able to sort out all the things that he wants to.
"Obviously we will miss him on the front bench."
Speaking on a visit to Warwickshire College in Rugby, Mr Balls said he wanted to show people there was an alternative to the coalition's "reckless and deep" cuts.
He said: "The first thing to say is that I did not want this job in these circumstances.
"I think it's been a real blow to the Labour Party to lose Alan Johnson, all of our thoughts are with his family.
"I just hope he will have the privacy to get things sorted out without the full media glare because that is the right way to do things."
He said he wanted to "hit the ground running" in his new job: "For me this is a very important job, I am keen to hit the ground running.
"We are here in a college which is training apprentices but also in a partnership with the regional development agency in the West Midlands which is going to be abolished by the Conservative coalition.
"These cuts in this way are reckless and deep and I think very dangerous for our economy.
"It's very important for me to say to the country with Ed Miliband, on the basis of the policies which we have all drawn up, 'look, there is an alternative, there is a better, fairer way to do this which will actually be a better way to get the deficit down by putting jobs and growth first, and that is what we are going to do'."
Mr Balls also had an answer for those opponents who were quick to exploit his close association with the economic policies of the Gordon Brown years.
He said: "I think the reason why a year ago unemployment was coming down was because Gordon Brown and Alistair Darling, in the face of a global financial recession, made the right calls.
"And over the last 13 years did we get everything right? Of course not, but Bank of England independence; not joining in the single currency, investing in the health service, bringing young people into work, those were what people wanted to see in our country.
"And now, to see deep reckless cuts from a Conservative Liberal coalition which put those jobs at risk, unemployment now rising, I think it's very important that we set out a very clear alternative and that's what I am going to do.
"We're here in a college where I have been talking to students doing catering, doing engineering, and they are going to be losing their Education Maintenance Allowance even though the Conservative education secretary Michael Gove said that would not happen.
"We're dealing at the moment with inflation going up, with a rise in VAT which wasn't going to happen according to David Cameron and Nick Clegg before the general election.
"These broken promises, they are an issue, but the biggest thing is the reckless, deep way in which the cuts are happening.
"It's taking a risk with the economy, with jobs, it's not necessary, it shouldn't be done in this way.
"Ed Miliband and Alan Johnson set out a very clear strategy in the last few months which I am carrying on to show that Labour has got an alternative, a responsible, tough but more sensitive way to deal with it which is better for jobs and growth.
"I think that is what people want to hear, that is what I am going to set out."