Zac Goldsmith and Sadiq Khan battled it out over London's transport system just hours before nominations closed for the City Hall election in May. The Conservative and Labour hopefuls clashed over Transport for London fares, with Khan promising a freeze to 2020 and Goldsmith pledging to bring in new money to "bear down" on the fees.

The Labour candidate claimed his manifesto commitment will cost £450m ($645m) over four years and promised to make efficiency savings to the "bloated" TfL. But the company has warned the actual cost of Khan's fares freeze will total £1.9bn.

"This pledge cannot be met without devastating our transport network, cutting police funding or hiking council tax to record levels – something Khan has explicitly refused to rule out," Goldsmith said.

"With London growing faster than ever, I am not prepared to experiment with our city's future by cancelling vital investment."

Goldsmith wrong on Night Tube?

But the Conservative manifesto also faces questions over its accuracy. Goldsmith claimed Khan and Labour leader Jeremy Corbyn's union backers are opposed to the Night Tube, a 24-hour service which will run across four major lines on Friday and Saturday nights.

In fact, three out of the four unions on the network – Aslef, the RMT and the TSSA – have voted in favour of the Night Tube. Unite, which represents 600 engineers and maintenance staff, is hoping to hold further talks with Underground bosses.

Goldsmith is also reiterated his opposition to a third runway at Heathrow Airport after the Airports Commission backed such a move, claiming the expansion could boost the British economy by £147bn and create 70,000 jobs by 2050.

"I will ensure Heathrow expansion stays absolutely off the table. London's prosperity depends on our being connected to the world — particularly those emerging markets where new business and jobs will come from," the Tory MP argued.

"As a Conservative, I support competition and choice for London's consumers rather than a vast, taxpayer-subsidised monopoly on one edge of our city."

The latest opinion poll from ComRes for ITV London, of more than 1,000 people between 14 and 17 March, put Khan six points ahead of Goldsmith in the second round of voting (53% versus 47%).

The Mayor of London candidates

  • Sadiq Khan (Labour)
  • Zac Goldsmith (Conservatie)
  • Sian Berry (Green)
  • Caroline Pidgeon (Liberal Democrat)
  • Peter Whittle (Ukip)
  • George Galloway (Respect)
  • Sophie Walker (Women's Equality Party)
  • Paul Golding (Britain First)
  • Winston McKenzie (English Democrats)
  • David Furness (BNP)