The Disasters Emergency Committee (DEC) said the scale of the disaster meant the need for aid was "immediate and vast".

The committee, whose members include British Red Cross, Christian Aid, Oxfam and Save the Children, said the money would be spent on both immediate relief and long-term reconstruction.

DEC chief executive Brendan Gormley said: "Our members are there and need the UK public to show huge generosity to help them reach those thousands of people who have seen their lives and livelihoods uprooted by this disaster."

Cyclone Nargis smashed into Burma on Saturday, bringing winds of up to 120mph, and leaving up to a million people homeless. Official figures put confirmed deaths so far at 22,000 but some 40,000 people are believed missing.

The appeal came as Foreign Office Minister Lord Malloch Brown warned aid to the south-east Asian country will not be effective unless the ruling junta opened up the country more to international rescue teams.

And human rights group Burma Campaign UK warned unless agencies were allowed in, more lives could be lost from hunger and disease than from the cyclone itself.

The military junta has agreed to accept help from the international community, but questions remain over how much access foreign rescuers will be allowed to the country.

Lord Malloch Brown said the Burmese government wanted to take care of matters itself, telling MPs on the Foreign Affairs Select Committee: "As of this moment even the initial UN assessment teams have not been granted visas to enter the country."

Burma Campaign UK director Mark Farmaner said: "We are five days into the disaster and most people have still not received any aid. If this carries on, more lives will be lost from hunger and disease than from the cyclone itself."