Sky has joined the BBC in deciding not to broadcast a charity appeal for Gaza, despite mounting political and public pressure for them to do so.
BBC boss Mark Thompson has again defended the decision, saying it would jeopardise the BBC's impartiality.
Sky News said running the Disasters Emergency Committee advert was "incompatible" with its objective role.
About 60 MPs say they will back a parliamentary motion urging the BBC and Sky to run the appeal.
Sky News had been considering the DEC film, and only reached its decision on Monday, hours before the appeal is due to go out on ITV, Channels 4 and Five.
John Ryley, head of Sky News, said: "The conflict in Gaza forms part of one of the most challenging and contentious stories for any news organisation to cover.
"Our commitment as journalists is to cover all sides of that story with uncompromising objectivity."
Criticism over the BBC's decision not to air the appeal has come from archbishops, government ministers, charity leaders and 11,000 viewers.
The DEC, which represents more than a dozen aid agencies, is asking for money to buy food, medicine and blankets following the Israeli assault on Gaza.
Pressure has been mounting on the publicly-funded BBC to air the appeal, but the director general reaffirmed his stance on Monday morning.
Mr Thompson said the BBC could not give the impression it was "backing one side" over the other.
He said the DEC had acknowledged from the outset there might be problems airing the appeal on the grounds of impartiality, and it was not the first time the BBC had decided against running an advert on their behalf.
He denied his "arm had been twisted" by pro-Israeli lobbyists and said the BBC would continue to cover the humanitarian dimension of a "complicated and deeply contentious story".
Labour MP Richard Burden, who is putting forward the early day motion, said he was "equally angry" at Sky News and the BBC, who were not being asked to broadcast a "political appeal".
"This is a humanitarian appeal from some of the most respected aid charities in the UK," he told the BBC. "It is about saving lives.
"If they (the BBC) want to maintain impartiality, then they should act without fear or favour and treat that child in Gaza just the same as a child in Congo, Darfur or the earthquake in Pakistan."
Journalists' unions the NUJ and BECTU said the BBC's justifications appeared "cowardly and in danger of being seen as politically motivated".
"Far from avoiding the compromise of the BBC's impartiality, this move has breached those same BBC rules by showing a bias in favour of Israel at the expense of 1.5 million Palestinian civilians suffering an acute humanitarian crisis," they said in a statement.A string of politicians, including International Secretary Douglas Alexander, Communities Secretary Hazel Blears and opposition spokesmen, have urged the corporation to reconsider its position.
Their comments drew criticism from BBC Trust chairman Sir Michael Lyons who said some were "coming close to constituting undue interference in the editorial independence of the BBC".
John Whittingdale MP, Conservative chairman of the Commons culture select committee, backed Sir Michael and defended the BBC's right to make its own judgement.
"It's very dangerous when you get ministers - members of the cabinet - telling the BBC to do something and reverse a decision," he added.
The Church of England also waded into the row, with the Archbishop of York appealing for the BBC to consider humanity, not impartiality, and show the film.
However, shadow culture minister Ed Vaizey said the BBC was right to be cautious, saying it had not broadcast appeals during conflict in Lebanon, Georgia or Chechnya.
"The BBC very rarely, if ever, broadcasts an appeal from a war zone," he said. "It's done it from areas where you could argue there's a civil war - like Congo and Rwanda - and of course it's done it for natural disasters.
"But the trouble with broadcasting an appeal from a war zone is that there are two sides to the argument - and that's what I think we're seeing here."
The UN Relief and Works Agency (Unrwa), the largest humanitarian actor in Gaza, said there was a "huge and overwhelming need" for aid.
Unrwa spokesman Chris Gunness told BBC Radio 4's Today programme that the situation in Gaza was a "political crisis with grave humanitarian consequences".
He said the estimated cost of "rehabilitation and repair" was $345m (£257m), with $230m (£167m) unfunded.
"We are massively underfunded, and I think the figures involve illustrate the sheer scale of the need involved here," he said.
Meanwhile, the activist group Stop the War Coalition have called for a protest against the decision not to broadcast the appeal outside BBC Broadcasting House in central London .