He called on elderly householders in Chesterfield, Baslow and Chapel.

He told residents he was investigating a robbery where someone had been arrested for stealing a large sum of cash in the area.

He flashed a card with a photograph on it claiming it was a police warrant card. He managed to steal from one of his victims, but others sent him away.

The calls on Tuesday were in Thirlmere Road, Windermere Road and Racecourse Road, all in Chesterfield, plus Main Road in Cutthorpe and Bubnell Lane, Baslow. He left when challenged at all those homes.

But when he called on an 83-year-old man in Hayfield Road, Chapel en le Frith, he stole two wallets containing cash and various bank and debit cards.

'Vulnerable people'

Police hope people leaving the Federal Mogul factory may have seen the bogus officer leave in a silver coloured Vauxhall, possibly a Vectra, which he drove the wrong way down Town End and back onto Hayfield Road.

He was described as white, in his 20s, around 5 ft 7 ins, of slim build and with short dark hair, wearing a dark sports or suit jacket and dark trousers.

DS Simon Beale of Derbyshire police's Operation Liberate unit, which focuses on distraction burglary and bogus official offences, said: "In these cases we are looking at the incidents all being linked.