Detectives are hunting a pair of pensioners posing as good Samaritans, who have stolen thousands of pounds from bank customers after pelting them with excrement.

One victim was robbed of £1,500 after being hit on the back of the head by a handful of foul-smelling waste.

Detectives leading the investigation said it was one of the most unusual and unpleasant crimes they had dealt with.

Even more bizarrely, the attackers were not teenage "hoodies" or hardened gang members but an elderly man and woman of Eastern European appearance.

Police are sifting through street security camera footage in a bid to hunt down the filthy thieves, who are believed to be stealing cash while they pretend to help clean up their victims.

The strange distraction tactics have been used on customers leaving banks in North Street, Brighton.

The latest attack took place on Thursday, when a man was robbed of £1,500 after leaving Barclays bank. He was walking through Castle Square when he felt something hit him on the back of the head.

A man and a woman immediately offered to clean him up and the victim later discovered his cash was missing.

The man was described as Eastern European, 65 to 70 years old, 5ft 6in and of stocky build. He wore a dark cap and a dark quilted jacket.

The woman was about the same age and also Eastern European. She was stocky and wore a headscarf and quilted jacket.

On Valentine's Day, a woman described as Italian-looking and speaking very little English stole £6,000 from a woman who had walked into a shop in North Street after excrement was thrown at her.

The suspect followed her into the shop, saying she was also a victim.

Inspector Simon Starns, of Brighton police, said: "It is quite bizarre. We had an incident about a year ago in one of the sports shops in Brighton where peanut butter was put on someone as a distraction technique.

"The person was captured on that occasion. This seems like the work of a co-ordinated group."

He said anyone who suffered a similar attack should not seek help from passers-by but should speak to shop security guards or pub door staff, as well as calling 999.

Under the Shopwatch scheme, shops and bars have radio links to officers who can monitor CCTV.

Insp Starns said: "People need to keep up their vigilance."

Anyone with information should call Det Con Natalie Whitmore, of Brighton CID, on 0845 6070999.