Labour leader Ed Miliband has been forced to deny any involvement in attempts to smear opponents amid claims that "damaging" emails could have been sent by him to one of the key figures in a plot to attack senior Tories.
The claims from Gordon Brown's former spin doctor Damian McBride threatens to overshadow the Labour Party conference despite Mr Miliband's efforts to seize the initiative by announcing he would scrap the "bedroom tax" if he wins the 2015 general election.
A spokesman for Mr Miliband said:
Ed was not involved in any plan to smear or spread lies about opponents. Any suggestion he was is totally untrue.
More top news
David Cameron said the June 23 referendum is the most important vote young people will place in their lifetimes.
Plan would leave steelworkers worse off in retirement - but not as worse off as those in other pension schemes.
Donald Trump has labelled Hillary Clinton "crooked" and says he cannot wait to face her in November's US presidential election.