It emerged on Tuesday that the party's general secretary Margaret McDonagh had written confidentially to broadcasters accusing them of "inciting and colluding with" anti-government protesters on the election trail.
Labour have attempted to draw a line under the row and shift attention to their proposals for an NHS "university" and a pledge to recruit thousands of extra staff.
But the Conservatives, launching their manifesto for pensioners, and the Liberal Democrats, pushing their claim to make a real difference in government, both sought to capitalise on their opponent's discomfort.
Chancellor Gordon Brown did not answer a reporter who suggested Ms McDonagh's letter had been deliberately leaked to deflect attention from his refusal to rule out increases in national insurance contributions.
He again told his party's election news conference that he would not give such a commitment.
" There was never any attempt to influence the broadcasters' agenda... we have made our point "
Challenged about the accusations against broadcasters he read out a statement issued by Ms McDonagh.
It said "we have made our point" after raising concerns over the safety of staff and public with broadcasting companies.
But Liberal Democrat leader Charles Kennedy said of Labour: "What on earth are they so thin-skinned about? They're pathetic."
Conservative Party vice-chairman Tim Collins accused Labour of "thuggery and intimidation".
" They've now disguised the shambles they've got into by deciding it's all the fault of the media "
Michael Portillo on Labour's campaign
In her letter to the BBC, ITN and Sky News, Ms McDonagh said she had "growing evidence that broadcasters have been inciting and colluding with protesters at campaign visits by senior politicians".
The broadcasters have met Ms McDonagh to discuss her concerns, but all have denied the accusation.
One of the accusations centres on the prime minister's visit to a Norfolk hospital when a farmer, given a lift by the BBC and wired up with a microphone, moved in to ask a question.
A BBC spokesman said: "This was an ordinary voter who wanted to put a question... but we were upfront about this and spoke to a Labour Party press officer. There was no question of collusion."
Tony Blair said Labour had been dealing with concerns brought to their attention "and the matter's closed as far as we are concerned".
He preferred to concentrate on the launch of a series of Labour proposals for the future of the NHS.
Highlights include a new NHS university to boost the skills of 100,000 health staff and the recruitment of 20,000 extra nurses and 10,000 more doctors.
Speaking later on BBC Radio 2's Jimmy Young show, Mr Blair insisted that using the private sector to help the NHS, something which had been opposed by Labour in the past, was "not privatising it".
The prime minister also refused to be drawn on whether Labour would raise national insurance.
But he did say Labour has "no intention of harming incentives for people in the upper income bracket".
Launching the Conservative proposals for pensioners, including a pledge to increase the basic state pension, shadow chancellor Michael Portillo said it was based on promoting "dignity" for older people.
The tax system would be made "simpler and fairer" for pensioners and people would be encouraged to save for old age throughout their life.
The Lib Dems drew attention to their work in the Scottish Parliament and Welsh Assembly to back their claim to be able to make a difference in government.
Leader Charles Kennedy said his party now had "more representation and more power" than at any time since the days of Lloyd George while the Tories were "the weakest opposition for more than 100 years".
Meanwhile, William Hague's leadership of the Tories is coming under scrutiny from two directions.
A poll for BBC News Online suggested he is trailing Tony Blair by 31 points in the popularity stakes, putting him neck and neck with Mr Kennedy.
But he was given a strong endorsement by Conservative former prime minister Lady Thatcher in a newspaper interview.