Bristol is a step closer to getting a high-speed link up to London and Europe after the Government confirmed it is considering creating a £4.5-billion international rail interchange at Heathrow.

Detailed plans that divert the Great Western main line through to the London airport, which would allow passengers to transfer to the Eurostar line, are being considered by the Department for Transport.

Until now Government's plans had focused on creating a controversial third runway at Heathrow to expand air travel capacity while the Conservatives proposed an overhaul of the rail network to allow passengers to travel to the country's other major airports instead.

Now Transport Minister Lord Adonis has indicated he wants to push forward with both plans.

He said: "It makes good sense to plan improvements to Heathrow and the rail system together.

"I think that it's an attractive idea. It's vital we have an integrated approach to planning new rail capacity and any new airport capacity that's also required."

Engineering consultancy Arup's proposal includes a 12-platform station built on the northern boundary of Heathrow, operating direct high-speed services to the continent and major English cities such as Bristol and a link around London to the Eurostar line. It would make the station the largest in the UK.

A DfT spokesman confirmed it was considering the scheme along with electrification of the Great Western line to Plymouth.

Last year the Tories said they would scrap the third runway scheme and instead unveiled a package of measures that included creating a rail spur at the London end of the Great Western main line, ending the need for passengers to change at Paddington.

Although the party had not finalised details Shadow Transport Secretary Teresa Villiers said she would expect it to be in place by 2027.

But she criticised the Government for considering linking up train plans with the Heathrow expansion.

"A new rail hub at Heathrow should be an alternative to a third runway not a sweetener for it," she said.