In a letter to the BBC, Sky and ITV, Alexander expressed his “disappointment” that the appeal would not be broadcast.
The BBC refused to broadcast the humanitarian appeal for Gaza on the grounds that it did not want to risk public confidence in its impartiality.
The decision meant that other broadcasters also refused to air the appeal by the committee, the umbrella group for 13 aid charities.
A BBC spokesperson said: “The 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 [a] news story.”
In his letter Alexander said: “I write to express my disappointment at your decision not to support the Disasters & Emergency Committee (DEC) Gaza Crisis Appeal. I met with DEC, along with other NGOs and charities, yesterday to discuss their and the British government’s humanitarian response.
“As you know, the support of broadcasters is highly effective and extremely valued by the group of charities and NGOs who provide humanitarian relief under the DEC umbrella.”
Alexander offered to mediate between the charities and the broadcasters. “I understand from a statement issued to the press by the BBC that ‘the decision was made because of question marks about the delivery of aid in a volatile situation’.
“I stand ready to facilitate discussions with NGOs and charities to seek to address broadcasters’ concerns on this point. The situation is developing on the ground and I understand that Oxfam, Save the Children and others have been able to get some aid into Gaza today.”