The government faces the threat of being sued by Heathrow operator BAA over its decision to rule out a third runway at the London hub.

The company reportedly thinks it has a good case to get the Coalition to consider the expansion after consulting lawyers.

BAA believes there is a precedent for the government to change its mind as two councils mounted a successful judicial review a decade ago against Labour’s refusal to consider the case for expanding Gatwick, the Mail on Sunday reported.

The airport operator believes that the government’s refusal to consider the building of a new runway would be in breach of “proper process,” according to company sources quoted by the newspaper.

All options, including extra runways at Gatwick and Stansted and a new Thames Estuary airport, are being seen as legitimate subjects for discussion under the government’s delayed aviation policy review with the exception of a third runway at Heathrow which is being opposed by transport secretary Justine Greening.