LONDON (REUTERS) - Britain should build a new runway at London's Heathrow Airport, according to a recommendation by a government-appointed Commission into the country's airport capacity that could cause a political headache for Prime Minister David Cameron.

After a three-year study, the Airports Commission selected a new runway at Heathrow over two other shortlisted options, arguing this offered Britain the best way of adding long haul routes to new markets which it said were "urgently required".

"Heathrow ... provides the greatest benefits for business passengers, freight operators and the broader economy," said the Commission's chairman Howard Davies on Wednesday.

It is now up to the government to decide whether to accept the Commission's recommendation. Mr Cameron told voters in 2009, before he came to power, that a third runway at Heathrow would not happen under his watch, "no ifs, no buts".

The Heathrow recommendation was accompanied by a package of measures to try to limit the noise and environmental impact of a new runway, in an attempt to allay concerns which in the past have prompted protest and political division.

Lawmakers broadly agree that south east England needs a new runway to remain economically competitive, but building one near densely-populated west London is a politically toxic issue which in 2010 led to the scrapping of a previous expansion plan.

The Commission had considered two other options for expansion, shortlisting two options at Britain's busiest airport Heathrow, which is operating at 98 per cent capacity, and one at number two airport Gatwick.

Heathrow's largest shareholder is Spanish infrastructure firm Ferrovial.