London's Garden Bridge appeared doomed today after Sadiq Khan refused to sign crucial pledges over maintenance costs.

A guarantee from City Hall to bankroll the annual £2-3m bill was a key planning condition imposed by Westminster and Lambeth councils.

But London's mayor today refused to honour the pledge made by predecessor Boris Johnson.

The Garden Bridge Trust argued the maintenance guarantees where hypothetical because an endowment fund would cover the annual costs.

Mr Khan said the £185m project was too risky because of spiralling costs.

A recent report by Labour MP Dame Margaret Hodge, commissioned by the mayor, called for the idea to be scrapped even though taxpayers would lose £45m.