Thieves are stealing an average of three bicycles a day in Brighton and Hove.

The spate of thefts includes 47 bikes stolen from the North Laine area of Brighton during the past six weeks.

Some thieves are so brazen they carry bolt-cutters with them to remove locks.

With some machines valued at more than £1,000, police calculate that thieves have made off with about £70,000 worth of bikes during the past three months.

Now Sussex Police is launching a campaign urging cyclists to lock up every time they leave their bikes unattended.

"Trap bikes" that can be traced by police are being left around the city in the hope that they will be stolen so detectives can see where they are being taken and arrest the thieves.

Crime reduction manager Paul Knight said: "The number of bikes stolen accounts for a large amount of the thefts we see in the city.

"The aim of the trap bikes is to reduce the number being stolen and to arrest those responsible."

Police officers will be offering free advice and anti-theft measures to cyclists at The Level, Brighton, from 9.30am to 3pm, on Sunday, July 23.

People will be able to pick up stickers warning thieves that trap bikes are in use in Brighton and Hove.

They can also have their postcodes stamped on to the frames of their bikes for free.

Mr Knight said cyclists should use D-shaped locks that cannot be cut by bolt-cutters.

He said: "Wherever possible people should lock their bike to something solid and in view of a CCTV camera.

"If your wheels come off easily remove the front wheel and lock it to the frame and back wheel, using a second lock if necessary.

"Keep a list of the make and model of your bike along with details of the frame number its colour and any accessories or special features."

Andy Coakley has owned Freedom Bikes in George Street, Brighton, for 14 years.

He said more and more people were taking up cycling to get through traffic, fuelling a sharp increase in thefts.

He said: "There has been a definite increase.

"A lot could be stolen for parts because once they've been stolen they never come back to Brighton again.

"So many bikes are taken when people pop into the shops or leave them outside a friend's house.

"People need to realise they just can't do that.

"You'd be surprised at the number of people who have really expensive bikes and lock them up with chains from the pound shop that really aren't up to the job."