Zac Goldsmith and Sadiq Khan both failed to show at a London Mayoral hustings on Monday evening, organised to debate infrastructure priorities for the capital including transport. The two front runners in the race for City Hall were conspicuous by their absence and left it to Conservative Transport Minister Claire Perry and Labour’s London Assembly Transport Chair Valerie Shawcross to represent the two candidates.

Loud applause greeted an audience member who asked if the pair’s no show indicated that Messers Goldsmith and Khan are likely to dodge big questions about infrastructure if elected next month.

Three other Mayoral candidates – Caroline Pidgeon for the Liberal Democrats, Sian Berry for the Greens and Peter Whittle of UKIP – gamely set out their transport priorities at the event hosted at the Institution of Civil Engineers in Westminster.

Caroline Pidgeon pledged to continue building Cycle Superhighways, extend the Bakerloo Line towards Bromley and improve surface transport links to existing airports around London if elected. She added that the London greenbelt must remain “untouchable” in the face of pressures to build new homes.

Sian Berry said she would reform the existing congestion charge with a pan London road charge and extend the ultra low emission zone to improve air quality. She also pledged to introduce ‘fairer’ fares for public transport and hit out at “hugely expensive” plans to build road tunnels under London.

Peter Whittle said local people living on the route of the planned Crossrail 2 should have a referendum on whether the scheme should be built and called for High Speed 2 to be scrapped. He also spoke out about the congestion and pollution caused by an increase in private hire vehicles on the capital’s roads.

In a statement, the office of Zac Goldsmith said the Conservative Mayoral candidate “had an unavoidable diary clash which meant he could not make the debate”. It went on: “He was obviously very disappointed to miss this, but Claire Perry was a great stand in who not only is an expert on infrastructure but has worked closely with Zac over rail devolution.”

A statement from the office of Sadiq Khan read: “Unfortunately Sadiq was not able to attend the debate and Val Shawcross attended and spoke on his behalf. However, Sadiq has made clear throughout the campaign that London desperately needs more capacity on public transport if we’re going to cope with a growing city, open up new sites for affordable homes and promote jobs and businesses.”

London’s Mayoral election is on 5 May.