A £4.5bn rail hub could be built at Heathrow airport in an attempt to offset the environmental damage caused by a third runway

Transport minister Lord Adonis said the government was keen on the proposal, which would cut journey times to the Continent from some British cities.

The Heathrow rail hub was originally proposed by the Tories as a possible alternative to extra airport capacity. But the government, which is expected to approve plans for a third runway and sixth terminal at Heathrow in the next two weeks, appears to eager to do both.

Plans for a 12-platform station, drawn up by Arup, have already been presented to the Department for Transport.