Conservative MP Zac Goldsmith has denied having conversations with ministers about delaying a decision to expand Heathrow in order to protect his campaign for London mayor.

Speaking hours before Prime Minister David Cameron was expected to announce a six-month delay in the decision process for airport expansion in the south east, Mr Goldsmith said he had been given "no indication" about what the Government planned to do, and that he was "studiously avoiding speculation".

The MP for Richmond and north Kingston has promised to resign if David Cameron approved a third runway at Heathrow, although he told journalists this week that he now regretted that statement.

Top Tories are thought to be keen to avoid a situation where Mr Goldsmith is running on the Conservative ticket in the mayoral elections just months after resigning as an MP for the party.

Speaking at a canvassing event in Purley on Thursday, Mr Goldsmith said: "I've not been given any indication of what the Government is going to be doing.

"You don't know what the Government is going to say and nor do I. I'm studiously avoiding speculation."

Asked whether he would be prepared to commit his support to a second runway at Gatwick, an option strongly backed by Labour mayoral rival Sadiq Khan, Mr Goldsmith said: "At the moment the choice is between Heathrow and Gatwick, and you're going to hear in a couple of hours what the Government's decision is. Obviously I don't know what the answer is going to be.

"Clearly out of the two, it has to be Gatwick, but I don't think it's necessarily the right choice.

But it's not for me to set the policy."

On a recent visit to the Surrey airport, Mr Khan claimed that a second runway could create 20,000 extra jobs in Croydon and the surrounding area.