Harlock said that although the British Government had been quick to respond, more funds were urgently needed, with only two weeks to go before the expected snow threatens thousands more people.
"Both the Government and aid agencies have been hit by one horrific disaster after another," he said. "It is possible that they expected the UK public to be even more generous."
So far, the public has given more than £30m through the Disasters Emergency Committee, and the Government has promised £33m, £23m of which has already been given. The Department for International Development has said that £30m will have been given by the end of this week.
Harlock said: "The UK public has been very generous. But what there hasn't been, by any means, is the same level of support from
governments and institutions around the world."
He cited as proof the response to the UN call for $500m as a baseline requirement - only 20 per cent of this has been received.
Meanwhile, Oxfam has added its own plea. It is rally-ing donor governments to "wake up to the looming humanitarian crisis".
A spokesman for DfID said that Hilary Benn, the international development secretary, had expressed his surprise last week that more aid had not been pledged.
The department would continue to look to see if there was a need, the spokesman said. "If there is a need, we will fund it," he added. "The Government is not expecting people to stump up, but we will expect people to give what they can in response."
Since the disaster, comparisons have been made between the response to the earthquake and that to the Asian tsunami, when the public donated an unprecedented £350m.
So far, fewer deaths have resulted from the earthquake than from the tsunami. But about three million people have been made homeless by the quake, compared with two million following the tsunami.