British Airways would move its headquarters to the continent if Heathrow was not expanded, GLA members were told today.

Representatives from British Airways, Virgin Atlantic and Easyjet gave their opinions on airport expansion, to the Greater London Assembly's transport committee meeting.

British Airways Airport Policy and Planning general manager Paul Ellis said it would be a "disaster" if a third runway was not built at Heathrow.

About 25,000 jobs at the Heathrow would be lost, hotels would close and freight services would collapse, he said. But if Heathrow was expanded then current job numbers would increase from 65,000 to 80,000.

"People tend to underestimate the effects it's (Heathrow) the jewel in the crown in terms of civil aviation in this country."

He added: "The Mayors entire strategy for London would be under threat," Mr Ellis said.

BA would probably move to the continent instead of risking an untried airport 30 or 40 miles away, he said.

Virgin Atlantic Government and External Affairs Officer Vanessa Tamms said, if Heathrow's capacity was not increased, Virgin would "stagnate" and the airport's services would decline. Passengers would start using Frankfurt and Paris airports and it would make London a less attractive place to locate a business, she said.

Paris had opened two new runways in the past two years and Frankfurt planned to open a new runway by 2006. Both these airports would have 50 percent more capacity than Heathrow by 2010, Mr Ellis said.

Transport Committee Chairwoman Lynne Featherstone said it seemed BA and Virgin Atlantic had a "Heathrow or bust attitude". If they didn't get what they wanted then they would go elsewhere, the Liberal Democrat member for Haringey said.

The Government earlier this year released a revised consultation paper on expanding existing airports, or building new ones, to cope with expected growth in passenger numbers.

Building new runways at Heathrow, Gatwick, Stansted, and Luton are included as options, along with building a new, four runway airport at Cliffe in North Kent.

Mr Ellis said if a hub was built from scratch it would require huge investment in housing and transport.

The policy makers had to take into account the economic risks of not expanding Heathrow, he said.

Mr Ellis told the committee a short runway at Heathrow would be environmentally viable. In the long term there would also need for expansion at Gatwick and Stansted.

Only smaller planes such as Boeing 737's would be used on the runway and there would be no night flights, he said.

By 2030 it was imperative that there was a new runway at Heathrow airport.

Virgin Atlantic Government and External Affairs Manager Chris Humphrey said Heathrow at present was "severely constrained."

"We would be a much bigger airline today if it wasn't for the constraints of Heathrow."

Virgin Atlantic did not believe there was a need to create a second hub.

Easyjet Business Development Manager Chris Essex said the airline supported a new hub in the southeast.

"We believe it should go broader than Heathrow." It was important all the needs of the southeast were examined and the focus wasn't just on Heathrow, Mr Essex said.