Staff at a building society have been urged to step-up security after it was raided for the fourth time in two years last night.

A knifeman walked into the Portman Building Society in East Street, Shoreham, just before 5pm.

He vaulted over desks and threatened staff before snatching £2,300 from the tills.

The raider then left the office and ran off through the cemetery of St Mary's Church on the opposite side of East Street.

Staff raised the alarm and the Sussex Police helicopter was scrambled to search for the knifeman.

Nobody was hurt in the robbery. It is the fourth time the branch has been raided in two years.

The last time, on January 23, a man also jumped over the counter and threatened staff.

Other Portman branches in Worthing, Lancing and Haywards Heath have also been robbed in the past few months.

A police spokesman said: "We have suggested that they step up their security.

"After the last raid in Shoreham they put in Perspex screens to provide a barrier. This time the suspect vaulted over the desk between the screens."

The knifeman was wearing a short blue jacket, grey woollen hat, navy blue jeans and white trainers.

Anyone with information is asked to call Shoreham police on 0845 6070999.