Neither Friends of the Earth, for which Mr Lees was campaigns director, nor the British embassy in Madagascar was told of his disappearance until Tuesday morning, more than 60 hours after he vanished.
Yesterday, 150 men with a helicopter and a tracker dog and two handlers were finally combing the 2,400-acre patch of forest near Fort Dauphin on the south coast of the island where Mr Lees was last seen on the late afternoon of New Year's Eve.
QIT Madagascar Minerals, a a joint venture between Rio Tinto Zinc and the Madagascar government, whose operations Mr Lees was investigating while on holiday in the area, has put its own staff and vehicles at the disposal of the search, which has been joined by his girlfriend, Dr Christine Orengo. But by nightfall there was still no sign of him.
Dr Orengo's sister, Yvonne, said yesterday: "It was not really until Tuesday afternoon that people began to be mobilised into the area."And Charles Secrett, executive director of Friends of the Earth, said: "The search proper, with the right equipment, only began on Tuesday."
Another Friends of the Earth source said: "The really precious days were lost".
Mr Lees flew to Madagascar on 14 December and joined Paul Hellyer, a photographer who had been there for a week, on holiday. They investigated plans by the firm to mine titanium ore from what FoE says is a particularly valuable and vulnerable stretch of forest.
They were due to leave last Sunday, but late on the Saturday afternoon Mr Lees revisited a patch of forest to do some more filming. Mr Hellyer, who last saw him "in very high spirits" at luchtime, said yesterday: "The day before, he had visited the area and found some chameleons and was very excited about them. He may have gone back to see if he could find them again."
He said that the campaigner had asked an Australian named David Shannon, who was staying in the same hotel, to accompany him but he had declined. He had set off in a four-wheel-drive with his local driver on the 15-mile, 90-minute journey. At about 4.30 pm, he went into the forest saying that he would return in half an hour. The driver waited five hours, then returned to town and raised the alarm.
A small-scale local search began next day, but Friends of the Earth say the local police did not have the four-wheel-drive vehicles essential for penetrating into the forest and confined most of their activities to questioning communities surrounding theforest. A few people went into the forest on foot, but the search was very limited.
Mr Hellyer said he and Mr Shannon alerted the police but decided they could do nothing more locally and that it was more important to alert the outside world. Mr Hellyer flew home to Britain; Mr Shannon tried to contact the ambassador.
But both the British embassy and Friends of the Earth were closed for the New Year's holiday and did not open until Tuesday. Mr Hellyer contacted Mr Lees's girlfriend after his arrival on Monday night and she rang the Foreign Office.
Lady Chalker, the Overseas Aid minister, and Peter Smith, the ambassador, both then intervened with the Madagascar government and the search was stepped up.
But the hunt has only deepened the mystery. The forest, a narrow coastal strip less than a mile wide, is hard to get lost in: locals say that all you have to do is to turn your back on the mountains clearly visible inland and walk to the beach.
Friends of the Earth says there are no dangerous predators, poisonous snakes or ravines there. At first they thought Mr Lees might have slipped in the dense undergrowth, broken a leg and be waiting for rescue, but as the days pass without sign of him that seems less likely.
His friends and colleagues are now pinning their hopes on reports that he had diarrhoea on the afternoon before his disappearance, and say he may have become ill and is being looked after by local people. But even the offer of a reward, substantial in local terms, has so far failed to find any trace of him.
Yvonne Orengo remains optimistic that he will be found alive, but as the days go by Friends of the Earth is becoming gloomy.
Some are beginning to question whether Mr Lees ever went into the forest - a question that use of the tracker dog may be able to answer - and wondering whether the campaigner fell foul of someone locally and has been murdered.