The BBC has refused to broadcast a national humanitarian appeal for Gaza, leaving aid agencies with a potential shortfall of millions of pounds in donations.

The Disasters Emergency Committee (DEC), an umbrella organisation for 13 aid charities, launched its appealtoday saying the devastation in Gaza was "so huge that British aid agencies were compelled to act".

But the BBC made a rare breach of an agreement dating back to 1963 when it announced it would not give free airtime to the appeal. Other broadcasters then followed suit. Previously, broadcasters have agreed on the video and script to be used with the DEC, with each station choosing a presenter to front the appeal, shown after primetime news bulletins.

The BBC said it was not the first time broadcasters had refused to show a DEC appeal.

The corporation said it had been concerned about the difficulties of getting aid through to victims in a volatile situation. The BBC, which has faced criticism in the past over alleged bias in its coverage of the Middle East, said it did not want to risk public confidence in its impartiality.

The DEC's chief executive, Brendan Gormley, said the decision could have a big impact on its appeal. "We are used to our appeal getting into every household and offering a safe and necessary way for people to respond. This time we will have to work a lot harder because we won't have the free airtime or the powerful impact of appearing on every TV and radio station."

DEC appeals have recently raised £10m for the Congo and £18m for Burma.

Gormley rejected the BBC's claim that it was difficult for aid to reach those in need, saying 100 lorries a day were entering Gaza. He challenged the corporation's concerns about impartiality. "We are totally apolitical and are driven by the principles of the Geneva conventions in terms of impartiality and neutrality. This appeal is a response to those humanitarian principles. The BBC seems to be confusing impartiality with equal airtime."

A BBC spokesperson said: "Along with other broadcasters, the BBC has decided not to broadcast the DEC's public appeal to raise funds for Gaza. The BBC decision was made because of question marks about the delivery of aid in a volatile situation and also to avoid any risk of compromising public confidence in the BBC's impartiality in the context of an ongoing news story. However, the BBC will of course continue to report the humanitarian story in Gaza."

ITV said: "The DEC asked all broadcasters if they could support the appeal. We (the broadcasters) assessed the DEC's requirements carefully against the agreed criteria and we were unable to reach the consensus necessary for an appeal."

Sky said: "We were considering this request internally when the DEC contacted us to let us know that the BBC had decided not to broadcast the appeal at this time. As, by convention, if all broadcasters do not carry the appeal then none do, the decision was effectively made for us."