Workers at Cityjet, the main airline at London City Airport, face redundancy as the carrier looks to cut costs.

But bosses have insisted planned “efficiency measures” will not affect the number of routes it operates at the airport.

The affected employees have now entered a period of consultation.

Anti-airport expansion campaigners seized on the news as evidence that the future of London City itself could be under threat.

John Stewart, chairman of HACAN East, said: “CityJet’s troubles ask further questions about the long-term future of the airport.

“When Crossrail is completed, Docklands will be within about half an hour of Heathrow.

“We hope the new Mayor will seriously examine the case for replacing City Airport with an environmentally-friendly development that can bring more jobs to the local area than the airport has ever done.”

It comes as the airport itself is set to go on the market. Owners Global Infrastructure Partners hope to raise as much as �1.25bn.

A CityJet spokesman said: “Over the last two years CityJet has significantly improved its performance due to a range of cost reduction and efficiency measures.

“The company is continuing to seek ways in which it can maintain its competitiveness in the market and this includes staff negotiations, amongst a variety of other initiatives.

“The negotiations may lead to a limited number of staff taking voluntary redundancy, but until the formal consultation process has been finalised CityJet is not in a position to confirm the number of staff that may be affected by any changes.”