Stern words from the county council prompted Luton borough council’s sudden shelving of a decision on the contentious proposed expansion of its airport, it has been revealed.

Luton borough council (LBC) has faced questions and criticism from campaigners, neighbouring local authorities and residents about a planned doubling of airport passengers to 18 million a year.

Of particular concern is that the council could not be impartial in determining the major scheme, as it owns the airport and has plugged the expansion through its own publicity.

Permission was expected to be granted at a meeting last Thursday but when the council suddenly announced the decision was being deferred, it did not give a full explanation of why the application was put on hold.

But it has now been revealed that Herts county council’s (HCC) cabinet member for community safety and planning, Cllr Richard Thake, sent a terse letter to the leader of the borough council pointing out HCC had “consistently raised procedural concerns that it may not be within the power of LBC to determine this planning application”.

Cllr Thake said that under the Planning Act 2008, the scheme might have to be determined instead by the Secretary of State for Transport, as the airport was seeking to increase capacity by at least 10 million per year.

Although he called for the matter to be resolved before the scheme was submitted, “this did not happen”.

He warned the borough council that, given questions raised about capacity, it risked a legal challenge and could “undermine confidence not only in any decision made but also in the two potentially responsible bodies – LBC and the Secretary of State for Transport”.

Cllr Thake urged the council to delay the process to allow legal opinion to be sought on capacity. He has also written to the Secretary of State for Local Government, asking him to intervene.

As a consequence LBC postponed its decision and has instructed a planning QC, John Steele, who specialises in aviation, to carry out a complete review of the application, and the airport’s capacity.

County councillor for Harpenden North East David Williams, who has spoken out about LBC’s conflict of interest, said noise from night flights was another issue that needed to be resolved.

Neil MacArthur, who runs campaign website HarpendenSky.com, hailed the postponement of a decision as proof that local protest action had been “successful”.