Airports operator BAA has been told by the Competition Commission that it must sell Stansted and either Glasgow or Edinburgh airports.
The airports operator has sought to legally challenge the commission’s 2009 ruling that it should offload three of its seven UK airports and has already sold Gatwick.
But the commission said its decision was “fully justified” and would publish its final verdict in May or June.
The commission said today that passengers and airlines would still benefit from greater competition with the airports under separate ownership, despite the government’s decision to rule out new runways at any of the London airports.
Chairman Peter Freeman said: “We remain convinced that the original decision to require BAA to divest three airports is the right one for passengers and airlines.
“Having examined the case closely, we are clear that many benefits will still arise without that expansion, by increasing competition and addressing detrimental effects from BAA’s common ownership.
“We found that, if anything since the report, there now appears to be greater capacity available which will increase the potential for competition between the London airports. The introduction of new ownership at Gatwick, whilst too recent for us to base any conclusions on, has also given a foretaste of the benefits competition can bring.
“There has also been no cause to alter our view on the need for either Edinburgh or Glasgow to be under separate ownership.
BAA said it would “carefully consider” the commission’s provisional decision before deciding how to proceed and restated its belief that there had been a “material change in circumstances” since the initial 2009 ruling.