"BAA will be required to sell Stansted Airport followed by Edinburgh or Glasgow Airport, the Competition Commission (CC) has confirmed today," the regulator said in a final ruling.

"This confirms the CC's earlier provisional view, which was published in March. The sales process will start in three months' time or sooner if undertakings are accepted from BAA in the meantime."

BAA, which runs six British airports including London Heathrow, said in response that it would consider seeking a judicial review.

"This decision would damage our company which is investing strongly in UK jobs and growth," said BAA Chief Executive Colin Matthews, arguing the sector had experienced significant changes since the CC's initial ruling in 2009.

"We have a responsibility to protect our shareholders' investment and we will now consider a judicial review of the Competition Commission's decision."

The CC had ordered the group two years ago to sell London Gatwick and Stansted, as well as Edinburgh or Glasgow airport, within a two-year timeframe.

But there were then a series of legal challenges by BAA to the ruling, which ended with the CC findings being upheld.

The airports operator, bought by Spanish construction group Ferrovial in 2006, subsequently sold Gatwick to US investment fund Global Infrastructure Partners for £1.51 billion in late 2009.

Copyright AFP (Agence France-Presse), 2011