The government had promised to announce its verdict on airport expansion before the end of the year but The Times reports that Cameron is to postpone the decision due to concerns about the impact on air quality of a third runway.

The Airports Commission, which was headed by Sir Howard Davies, has recommended building a third runway at Heathrow in preference to a second runway at Gatwick.

The Times says that a committee of ministers, which has been formed to make the runway decision, is due to meet later this week but this would give little time for the full cabinet to discuss the issue before parliament’s Christmas recess begins on December 17.

The Conservative party is severely split over the expansion of Heathrow with prominent opponents such as current London mayor Boris Johnson and mayoral candidate Zac Goldsmith both vocal critics of a third runway. Chancellor George Osborne is seen as being the biggest supporter of Heathrow expansion.

The House of Commons’ environmental audit committee last week released a report recommending that Heathrow should not be given permission to build another runway until it could show that it was able to meet pollution targets.