Boris Johnson "does not have a green bone in his body", according to Green Party candidate for London mayor Sian Berry.

Berry, who was formerly the party's female principal speaker, told ePolitix.com that the Green campaign for this year's mayoral race was better organised and better funded than in previous years.

She criticised Conservative Boris Johnson's environmental credentials, saying: "He rides a bike and I think that's about where it stops to be honest. I don't think he has a green bone in his body.

"He was with me in this advert that Greenpeace put out where we got together all the mayoral candidates and said we oppose Heathrow expansion, and then about a week later he comes up with this plan to build a whole new airport to the east of London," she said.

Johnson has proposed reviving plans to switch the capital's principal airport to the Thames estuary.

Berry, who stood in the 2005 general elections in Hampstead and Highgate, said she was campaigning on policies including a higher target for affordable housing in all new developments.

She is proposing plans to ensure all public employees are paid a "living wage", while private sector employees paying any less will be "named and shamed".

Berry has also pledged free housing insulation for all Londoners, in an extension of the current scheme which provides the service to some benefits claimants and pensioners.

She said the other parties had done a "disservice to the Green cause" by talking about responses to climate change only in terms of extra taxes.

"Stressing the fact that [the policies] are going to save you money is a way we hope of getting across that it's not all about green taxes," she said.

Berry added that she will use the campaign to educate voters about the single transferable vote system being used in May, which means that second preferences are likely to decide which of the front-runners becomes mayor.

"Your first vote is your own choice, it should be you vote for what you believe in," she said.

"The run-off is going to be on the second choice votes, that's where you put an insurance vote if you're worried about Boris getting in; if you really want to get rid of Ken."

While acknowledging that she faces a high-profile field of experienced politicians, she said: "I think eventually people will get very bored with the Boris and Ken show."