PARENTS are being warned to be on their guard after a couple claiming to be a social worker and a plain-clothes police officer tricked a small boy's mother into letting them talk to him.

The man and woman called at the family's home in Oakley Green, West Auckland, at about 5.30pm on Thursday, asking about an injury to a four-year-old boy.

Without asking for identification, the mother allowed them to speak to her son, although she stayed in the room during the interview.

The woman, who said she was a social worker, made notes during the conversation.

After spending about 45 minutes in the house, the couple left in a small blue vehicle, saying they would contact the family again.

Detective Constable Sarah Jackson, of Bishop Auckland CID, said: "We can only guess at the motives of these people and would urge parents to be alert to the possibility of bogus officials calling at their door.

"Genuine callers will be carrying identification and any unsolicited visitor should be asked to prove they are who they claim to be."

The woman was white, in her early 40s, 5ft 7in and slim, with blonde, shoulder-length, straight hair.

She was wearing a beige trouser suit and white blouse, black shoes and gold hooped earrings.

The man was white, of similar age, 5ft 10in, of average build, with short, dark brown hair. He wore black trousers, a white shirt and black clipped tie.

Anyone with information is asked to call police on (01388) 603566 or Crimestoppers on 0800 555 111.