The charity, which runs the capital’s only air ambulance, is warning Londoners against a bogus company claiming to collect donations for an air ambulance service.

London’s Air Ambulance, based on the roof landing pad at Whitechapel’s Royal London hospital, is urging people to be aware of a door-to-door company calling itself the ‘Air Ambulance Service’. This is not a registered charity and London’s Air Ambulance is not receiving any donations from this service, a spokeswoman said.

LAA has been alerted to this company collecting clothes and lottery money in the Wanstead and Eltham areas recently. “Clothes recycling and more so the lottery are valuable sources of income to the charity, who do employ door-to-door canvassers,” the spokeswoman said.

Charity Director, David Oakley, said: “We are quite angry that they are purporting to collect on our behalf.”

The spokeswoman added “The Charity would like to take this opportunity to tell people to be careful, but urge them to continue supporting and not hesitate to phone our fundraising office if they are unsure,” she added.

Earlier this month four men were arrested after police raided a depot in Essex as part of an investigation into charity bag collection fraud.

The City of London police seized second-hand clothes worth hundreds of thousands of pounds to charities in a raid on a suspected criminal gang. They also seized �20,000 in cash, along with charity bags, computers and correspondence. All four men were released on bail.

Charity bag fraud is estimated to be costing the third sector up to �50m each year, leading to the cancellation of vital aid projects.