Zac Goldsmith has promised to trigger a byelection if he is elected as part of a Conservative Government that breaks key election promises.

At a hustings organised by Richmond Chamber of Commerce, the Tory candidate for the Richmond Park seat, currently held by Susan Kramer, said he would not vote along party lines in the House of Commons if he felt any issue would have a negative impact on residents.

And when asked by host James Naughtie, who presents the Today programme on BBC Radio 4, if he would tell parliamentary whips to "stuff it"”if he disagreed Mr Goldsmith replied "absolutely".

He added: "There are various things I have said in this campaign with absolute certainty.

"I said there will be no Heathrow expansion under our Government, there will be no charges for parking in Richmond Park and Kingston Hospital will be safe.

"If any of those promises are broken I will trigger a byelection and allow people to penalise my party."

” Mr Goldsmith joined Ms Kramer and three other candidates for the Richmond Park seat - Labour's Eleanor Tunnicliffe, James Page from the Green Party and Peter Dul from UKIP.

The four candidates for the Twickenham seat - incumbent Liberal Democrat Vince Cable, Tory Deborah Thomas, Labour's Brian Tomlinson and UKIP's Brian Gilbert - were also at the hustings at Duke Street Baptist Church, Richmond, on Monday.

Hundreds of residents asked questions on topics ranging from electoral reform and the Lisbon Treaty to the tax system and the third runway at Heathrow.

The main row of the evening erupted over how much each of the candidates was spending on their election campaigns and all speakers explained why they should win the ballot.

Ms Kramer emphasised the need for a defence of Kingston Hospital amid fears departments could be shut, while Labour and Tory representatives said no such risk existed.

Ms Kramer also criticised Conservative policy to give tax breaks to married couples and said it would create first and second class families.

Dr Cable said a hung parliament would be good for the country as it would force parties to work together but denied he had plans to do deals with the Labour Party.

Mr Tomlinson said discussions about such things were wasted time”due to their rarity.

Ms Tunnicliffe said a vote for Labour was one to secure the economic recovery and Ms Thomas said the Tories had given commitments on public services, while Dr Cable said the parties should be judged on how they would deal with the economic problems.

Mr Dul said UKIP would withdraw Britain from the European Union and return powers to Parliament while Mr Page said the main parties were fighting over the middle ground and the Green Party offered something different.

Speaking on the subject of Heathrow expansion, Ms Tunnicliffe told voters she did not agree with the Government's stance.

She welcomed Lord Justice Sir Robert Carnwath's ruling last month that plans for a third runway at Heathrow were untenable and incompatible with the 2008 Climate Change Act.

She added: “"I have had to part company with our leader on the issue of Heathrow.

"I was pleased and quite relieved with the court decision.

"I don't agree we should have a third runway."”

Mr Page said he was delighted with the court ruling, while Mr Dul said UKIP approved of proposals for a new airport in the Thames Estuary.

Ms Kramer added: "We believe aviation has to pay its own environmental cost and these green taxes will be ringfenced into infrastructure and green proposals."”