An instructor who had £7,000 worth of surfing kites stolen from his car is warning they can kill in the wrong hands.

Simon Catling, 32, who teaches the new extreme sport of kite surfing at Hove Lagoon, spent years building up his collection of equipment.

Thieves broke into his car and made off with nine kites and outdoor gear while he was in Weymouth to compete in the first round of the British Kite Surfing Championships.

Kite surfing is predicted to be the hottest new sport on Brighton and Hove seafront this summer.

The sport is particularly eye-catching with surfers performing spectacular jumps as the boards are pulled across the surface of the sea, reaching speeds of up to 40 or 50mph.

Mr Catling, of Mile Oak, Portslade, said: "These kites can kill if the people who stole them don't know how to use them. You can be lifted high into the air and the lines are like cheese cutters - they can seriously hurt people. You need to learn how to use them properly and I am worried about what will happen to the reputation of the sport if there is an accident."

Mr Catling is also furious because the company he insured the contents of the car with, Abbey National, has refused his claim. All doors of the car were locked and it was parked on a private driveway.

The equipment was in a boot covered by a parcel shelf but Mr Catling lowered a back seat to accommodate part of a board, which he covered with a coat.

Abbey National said because the back seat was partially down, the car was not secure and it does not have to pay Mr Catling.

Mr Catling has paid £15 a month for the past two years for the insurance policy.

He said: "When I was thinking about taking out insurance, I told Abbey National I would be leaving kites in my car and they said that would be fine -they would be covered. Everything was locked up in the boot but obviously the board is too big to all fit in the boot. I am really angry they won't pay, especially because they approached me in the first place. I told them I would be leaving the kites in the boot and they promised I would be covered. Now I have got nothing. I am absolutely gutted - I built up my kit slowly while I was working in kite shops."

A letter from Abbey National to Mr Catling refusing his claim said: "The kites were placed in the rear of your vehicle along with the surfboard and the back seat was partially down thus rendering the boot not being fully enclosed."

The makes of the stolen kites are Manta, Blades and Naish.

A spokeswoman for Abbey National said: "The claim has not been accepted because the property wasn't hidden from view. The wording of the policy said it had to be hidden from view in an enclosed boot."

She said Mr Catling could go to the insurance ombudsman if he was not happy.