Eco activists have dismissed plans for an international rail hub at Heathrow as a 'cynical ploy'.
Transport minister Lord Adonis announced proposals for a £4.5 billion high-speed rail link, connecting London with Europe and northern England, at the weekend.
Anti-expansion campaign group HACAN said it welcomed the scheme, which it claims will cut the need for short-haul flights from the airport, but only as an alternative to a third runway.
"The Lord Adonis announcement is simply a cynical ploy to appease the opponents of Heathrow expansion and try to hurt the Conservatives, who said they would scrap expansion plans at Heathrow in favour of high-speed rail last autumn," said HACAN chairman John Stewart.
"The Government hasn't thought this through. It is simply cynical opportunism. We will not fall for it."
Lord Adonis said it was 'vital' to have an 'integrated approach' when planning extra capacity for rail and air travel.
Tory transport spokeswoman Theresa Villiers claimed better rail links could cut the number of flights to and from Heathrow by 66,000 a year, nearly a third of the planned capacity of a third runway.
The Government is expected to announce its verdict on Heathrow's expansion before the end of the month.