World airlines are shunning the UK due to capacity constraints at Heathrow Airport, according to a survey.
As many as 53% of scheduled airlines have either decided to, or are preparing to, base flights in other countries than the UK because of Heathrow's lack of capacity, the poll showed.
And 86% of airlines said they would put on more flights to the UK if additional take-off and landing slots were available at Heathrow, the survey from the Board of Airline Representatives in the UK (BAR UK) revealed.
The survey results are being released today at a transport conference in London by Colin Matthews, chief executive of BAA, which runs Heathrow.
He is one of the airline and industry chiefs anxious for the Government to reverse its policy and give the go-ahead for expansion at Heathrow.
In a speech at the London conference today, Mr Matthews will say: "These figures show that it is a mistake to believe that flights displaced from Heathrow will automatically fly to Stansted, Gatwick or Birmingham instead.
"The message I hear from airlines is clear: if there's no room at Heathrow then flights will move out of the UK altogether."
He went on: "Instead of Britain taking the lead in forging new links with growing economies like China, we are handing economic growth to our competitors by turning away airlines who want to bring jobs, growth and trade to the UK."
Mike Carrivick, chief executive of BAR UK, which represents 84 scheduled airlines, said: "UK business leaders should be very concerned about the restrictions on reaching new markets at such a critical time in the UK recovery effort.
"The survey's results are a chilling reminder that the Government must act decisively, and soon, in the national interest. Restricting capacity at key airports to the same level as the last decade is actively encouraging airlines and trade to go elsewhere."
Aviation Minister Theresa Villiers said: "We recognise the importance of maintaining Britain's position as one of the best-connected countries in the world.
"That is why the Chancellor committed us to exploring all the options for maintaining the UK's aviation hub status, with the exception of a third runway at Heathrow.
"We are also pressing ahead with action to improve the way our airports operate today, with modernisation of economic regulation, aviation security and airspace management.
"The debate on the long-term transport needs of the economy is immensely important and I would urge everyone in the industry to take part when we publish our forthcoming consultations on a sustainable future for aviation."
Speaking at the London conference today Katja Hall, the CBI's chief policy director, said: "The 11 major policy reviews on airport capacity since the last full-length runway was opened in the south of England in 1948 illustrate the degree of political challenge here. But the consequences of this indecision can no longer be ignored.
"The UK is becoming a branch-line destination on the route map of global airlines. This is a damaging break in the UK's export chain, and its consequences are a real concern for businesses across the country.
"We need to act now to ensure the UK remains a world-class business destination, and lay a key building block for achieving increased trade with high growth economies."