The BBC was in crisis last night as politicians including government ministers, religious leaders and senior members of its own staff condemned the decision not to broadcast a charity appeal to help the stricken people of Gaza rebuild their homes.

The corporation's director general, Mark Thompson, was left isolated as rival broadcasters ITV and Channel 4 agreed to put out the plea for aid made jointly by 13 British charities. The BBC has decided the broadcast of the appeal might be seen as evidence of bias on a highly sensitive political issue.

The Archbishop of York, John Sentamu, has accused the broadcaster of "taking sides". He said yesterday: "This is not a row about impartiality but rather about humanity.

"This situation is akin to that of British military hospitals who treat prisoners of war as a result of their duty under the Geneva convention. They do so because they identify need rather than cause. This is not an appeal by Hamas asking for arms but by the Disasters Emergency Committee asking for relief. By declining their request, the BBC has already taken sides and forsaken impartiality," the archbishop added.

Communities secretary Hazel Blears said: "The BBC's decision should not discourage the public from donating to this important appeal. I sincerely hope the BBC will urgently review its decision."

The BBC's unrepentant stance has stirred up rebellion in the ranks of it own reporters and editors. One senior BBC news presenter told the Observer: "I've been talking to colleagues and everyone here is absolutely seething about this. The notion that the decision to ban the appeal will seem impartial to the public at large is quite absurd.

"Most of us feel that the BBC's defence of its position is pathetic, and there's a feeling of real anger - made worse by the fact that contractually we are unable to speak out."

Jon Snow, the journalist who presents Channel 4 news, said the BBC should have been prepared to accept the judgment of the aid experts of the DEC. "It is a ludicrous decision. That is what public service broadcasting is for. I think it was a decision founded on complete ignorance and I am absolutely amazed they have stuck to it."

Snow said he suspected a BBC bureaucrat had "panicked" and he called upon Mark Thompson to put the situation right. Martin Bell, the former BBC foreign correspondent, said the BBC should admit it had made a mistake. He claimed "a culture of timidity had crept" into the corporation. "I am completely appalled," he said. "It is a grave humanitarian crisis and the people who are suffering are children. They have been caught out on this question of balance."

But Greg Dyke, Thompson's predecessor as director general of the BBC, said the issue put the BBC in a "no win situation". He added: "Outside of Iraq, the single biggest issue that caused complaints was the coverage of Israel. I can understand why the BBC has taken this decision, because on a subject as sensitive as the Middle East it is absolutely essential that the audience cannot see any evidence at all of a bias."

Douglas Alexander, the international development secretary, who has attacked the BBC's decision, today welcomed commercial broadcasters' decision to break ranks and urged the BBC to think again. "I welcome this decision. The DEC appeal is crucial to help alleviate the suffering of people injured, displaced and hungry in Gaza."

The BBC also faces demands for an explanation from within the Commons international development select committee. Richard Burden, the Labour MP and committee member, said the BBC was out of step with public opinion. Andrew Mitchell, the shadow international development secretary, who was this weekend making a visit to Gaza, Israel and the West Bank, said it was up to the BBC, but added: "We believe that they should allow the broadcast to proceed so that the British public, who have proved themselves so generous during recent emergencies in the Congo and Burma, can make their own judgment on the validity of the appeal."

The satellite broadcaster Sky said it was "considering" broadcasting the appeal.

A spokesman for the BBC said: "We do accept that people are strongly guided in their view on this by the humanitarian emergency. We are highlighting the situation in Gaza in every news bulletin and that is one of the reasons the issue is so high on the agenda."

Thompson received backing from the BBC Trust's chairman, Sir Michael Lyons. He said he was "concerned" about the tone of some politicians' comments on the issue, which he said came close to "undue interference" in the BBC's editorial independence.