Hotel giants including Travelodge, Holiday Inn, Crowne Plaza and Intercontinental Hotel Group have written to London Mayor Boris Johnson warning him that his “hotel tax” plan could put new developments in doubt.

Developers are due to contribute £600m towards Crossrail. Only office schemes were due to contribute but that has now been extended to retail and hotel schemes in central London and Docklands.

The hoteliers believe the levy would add between three and four per cent to the cost of a new hotel.

Travelodge has 17 sites it wants to develop in the next 10 years but says the levy would add £9m to its bill.

Chief executive Grant Hearn said: “With the Olympics set to raise London’s profile around the world, introducing a tax which will slow down the development of new hotels is counter-productive.”

Whitbread chief executive Alan Parker said: “This could cost us over £2m. It’s a last-minute change which has pushed up our construction budget by five per cent.

“We’re still going to go ahead because we’re committed, but we have to reclaim the money back somehow and unfortunately we’re going to have to pass on the extra cost to customers.”

The complaints came as Johnson warned that the future of Crossrail is not yet “signed, sealed and delivered” amid continuing fears the scheme could be scaled back or delayed.