The controversial UN chief who admitted lying about climate change knew about his error two months before announcing it, according to reports last night.

Last week Dr Rajendra Pachauri was forced into a humiliating climbdown over claims the Himalayan glaciers could vanish within 25 years.

He said he had only just learned his prognosis had been refuted by experts, after the report in which they were included formed a key plank of proposals at the Copenhagen climate change summit.

But last night it emerged he had been told he was wrong about his date of 2035 by leading glacier experts eight weeks before the summit began.

Most glacier experts believe the Himalayan ice is so thick and at such high altitude it would take at least several hundred years to melt and some glaciers are currently growing.