BAA has been criticised again by the Competition Commission for failures at Stansted airport.

The group, which also operates Heathrow and Gatwick, “acted against the public interest” by failing to manage queues at security and for not consulting with airlines on the development of the airport.

The Commission warned BAA could be fined if it cannot meet the standards.

BAA is already under pressure to break up its ownership of the three key London airports and may be forced to sell both Gatwick and Stansted.

Commission deputy chairman Christopher Clarke, said: “We believe our recommendations will provide the necessary incentives for BAA to meet existing and future customers’ needs by operating efficiently and by continuing to develop the airport.”

The Commission said it has received several submissions, from Ryanair in particular, that passenger security queue management has been poor.

Failing to provide enough staff at peak times was highlighted as a major problem at Stansted, which performs relatively poorly in customer surveys compared to other airports.

Ryanair also told the Commission the performance data provided to airlines did not reflect Ryanair’s own experience – suggesting the airport’s measurement of queue lengths was unreliable.