Campaigners have begun a new High Court action in their ongoing battle against expansion at Stansted Airport.

The Stop Stansted Expansion group (SSE) today lodged papers at the Royal Courts of Justice in London alleging that the criteria being applied to decide on possible options for new runway sites in England are “infected by apparent bias”.

SSE want High Court judges to order the Government-appointed Airports Commission to delay the publication of any shortlist of options until the criteria have been re-determined.

The group alleges there was apparent bias because Geoff Muirhead, a recently-resigned member of the Commission, had a conflict of interest.

Mr Muirhead is a former chief executive of Manchester Airports Group (MAG), the owners of Stansted since February.

He stepped down from the Commission three weeks ago after SSE warned Transport Secretary Patrick McLoughlin they would take legal action if he stayed.

SSE economics adviser Brian Ross said: “With proposals on the table from MAG to make Stansted the world’s busiest airport with four runways handling up to 160 million passengers a year, there is far too much at stake to allow the issue of apparent bias to go unchallenged.

“For almost a year, Mr Muirhead was allowed to play a pivotal role on the Commission as its only commissioner with first hand knowledge and experience of the aviation industry.”

Mr Ross said it was not enough simply to remove Mr Muirhead from the Commission “at this advanced stage”.

The High Court is being asked to order the Commission, chaired by Sir Howard Davies, “to re-visit certain key decisions made by the Commission during the time that Mr Muirhead was involved”.

The Department for Transport said Mr Muirhead had “acted properly” at the Commission but stood down to “avoid any perception of a potential conflict of interest”.

A DfT spokesman added: “Both the department and Sir Howard agree that there is no evidence whatsoever of bias and the Airports Commission is content that decisions taken to date are robust.”