Zac Goldsmith has claimed his record as an anti-Heathrow expansion campaigner means a vote for anyone else would make the third runway “inevitable”.

With less than a week to go until the Richmond Park byelection, Mr Goldsmith has insisted the proposed airport expansion is the central issue.

His Liberal Democrat opponent, Sarah Olney, also opposes the third runway.

He said: “The focus has been on Heathrow. The Liberal Democrats have massively played down the impact expansion would have on this area.

“I think they know that if people are voting in this election based on Heathrow there is only one sensible way to vote.

“The Liberal Democrats’ position is a passive one. If a vote comes up in Parliament they will vote against it, but not much else.

“In no way am I saying Sarah (Olney) supports the third runway, but that level of activity would mean Heathrow expansion would be inevitable.

“That is why I have the backing of the anti-Heathrow campaign groups.”

A Liberal Democrat spokesman refuted Mr Goldsmith’s claim, claiming that his party blocked Heathrow expansion when in coalition government.

The Liberal Democrats published the results of a survey of 3,500 constituents on Thursday, which showed 83 per cent believed Brexit would have a negative impact on local jobs, and 87 per cent thought remaining in the single market should be a priority.

Mr Goldsmith backed the Leave campaign in the referendum, while 72 per cent of Richmond Park constituents voted to remain in the European Union.

But he reassured voters by saying he has been a “moderating influence” in the debate.

He said: “I made two interventions as MP; I was one of only two Tory MPs to vote with Labour My to ensure EU nationals living in the UK could stay, and I voted to get EU environmental translated into UK law.

“I would like to see us get good access to the single market when we leave. I want us to get the best possible deal.”

The Richmond Park byelection follows an unsuccessful campaign by Mr Goldsmith to become London Mayor, which was labelled as “controversial” and “cynical” by opponents.

Asked whether it would impact this election, he said: “I regret I was unable to control the debate in the final weeks.

“But the outcome in West London in that election was good; I did better than any previous Mayoral candidate here.

“If that result was replicated across London there would have been a different outcome.”

Voters will cast their ballots in the Richmond Park byelection on Thursday, December 1.