Walsh told the Financial Times that expanding Heathrow, which serves as Britain's main hub, with a third runway offered the quickest solution to the UK's airport capacity crunch.

"I'll bet you that in 2050, British Airways will be flying from a two-runway airport at Heathrow," Walsh is quoted as saying.

"It is not that I lack ambition. It is that the people who we need to address these issues lack ambition, and lack the balls to take tough decisions in the interests of the long-term economic development of the UK."

IAG (ICAG.L) is the owner of British Airways and Iberia.

Expansion at Heathrow, owned by Ferrovial's (FER.MC) BAA and operating at about 98 percent capacity, has been ruled out by Britain's ruling Conservative party.

Walsh called on the government to reconsider their opposition to the expansion of Heathrow, which is falling further behind rival European airports in the battle for lucrative routes to emerging markets, according to a recent study.

He also said Britain needed a four-runway airport in the long-term, but acknowledged suburban Heathrow was unlikely to be the location.

Calls for a new international airport in south-east England at the Thames Estuary, often referred to as Boris Island, after its high-profile backer, London's mayor Boris Johnson, have gathered pace in recent months.

(Reporting by Stephen Mangan; Editing by Michael Urquhart)

• A Permanent Economic Emergency