Business secretary Vince Cable is set to headline a rally against a third runway at Heathrow, but trade leaders have criticised his slated appearance.

The Twickenham MP is among nearly 20 politicians and campaigners lined up to address the central London event being staged by anti-expansion pressure group HACAN on Tuesday (March 3).

Green Party leader Natalie Bennet, former Tory transport minister Steven Norris and Brentford & Isleworth MP Mary Macleod are just some of the other figures due to talk at the 700-capacity Church House Conference Centre, in Westminster, from 7pm.

But it is Mr Cable's presence which has riled Stephen Fry and Frank Wingate, chief executives of Hounslow Chamber of Commerce and West London Business respectively, which between them represent thousands of firms based around Heathrow.

Despite appearing in his capacity as a constituency MP for Twickenham, he was originally referred to on rally posters and leaflets by his cabinet position.

They claimed this breached the ministerial code of conduct, which requires ministers to keep separate their constituency and ministerial roles.

In a joint letter to Prime Minister David Cameron, questioning his billing, they wrote: "As representatives of thousands of businesses in west London, we consider the secretary of state's proposed appearance at this rally to be highly inappropriate when the prevailing opinion within the business community is to support expansion at Heathrow.

"If he wishes to attend as a constituency member that is his prerogative but he should not attend in his official capacity as business secretary."

'Mistake'

Mr Cable's office pointed out that Mr Cable had accepted the invitation via his constituency office and had never requested to be billed as business secretary.

They said they had contacted HACAN on Wednesday morning (February 25), as soon as they had become aware his ministerial title was being used to promote the event, and that error was corrected immediately.

Mr Cable also downplayed the row as a bit of mischief making by pro-expansion groups.

"I have no intention of being intimidated and will continue to speak up for my constituents, a large number of whom are opposed to a third runway," he said.

"There's no question of inappropriateness. I think the organisers simply made a bit of a mistake in describing me in my ministerial capacity rather than as a constituency MP."

Richmond residents, including those in Mr Cable's Twickenham constituency, have traditionally been the most fiercely opposed to expansion at Heathrow.

In a referendum organised by Richmond Council in 2013, 80% of voters opposed a third runway at Heathrow. A poll carried out by Populus for the airport late last year put opposition in Twickenham at 49%, with 13% undecided.

HACAN chairman John Stewart said: "This rally is intended to send a clear message to the next government: a third runway at Heathrow is politically undeliverable. The opposition remains huge. It is a cross-party movement with widespread popular support."

He described the row over Mr Cable's billing as a "storm in a teacup", which he said Back Heathrow had been "ferociously brewing".

Rob Gray, campaign coordinator of pro-expansion group Back Heathrow, which was set up with funding from the airport, said: "It is no surprise that business leaders are unhappy about Vince Cable's decision to attend the rally as secretary of state.

"It is a brutal kick on the shin to UK manufacturers and exporters who have expressed support for Heathrow expansion but Dr Cable just doesn't seem to care."

The Airports Commission is considering rival bids for a new runway at Gatwick and Heathrow. It is expected to make its final recommendations in June.