Unwitting Bradford householders have coughed up 'on-the-spot fines' for not returning Census forms - only to discover they have been targeted by an opportunist conwoman.

Police and Census chiefs today warned people to be on their guard against the scam, revealing it was the first time it had been seen in the country.

At least two households in the Shearbridge area have been targeted and officers are urging other would-be victims to come forward.

On Sunday at around 2pm, a 47-year-old taxi driver from Grantham Road handed over £20 to the woman, who is described as Asian, slim and around 20 years old.

Detective Inspector Chris Binns, of Bradford South Police, said: "The suspect knocked at the door and purported to be a Council worker. She asked the householder to pay a fine for failing to return his Census form and the man handed over some cash."

Around 15 minutes later, the same suspect struck again in nearby Spring Lane, this time taking £40 from a 54-year-old housewife.

Det Insp Binns said it was thought other residents may have been targeted, possibly in the Toller Lane area.

"We would ask anyone who has been approached to contact us. There may have been people asked who had returned the Census and so refused to pay. We would like to hear from them as well."

He said: "We would urge people not to hand over money to anyone claiming to be a Census enumerator as they have assured us that they never issue on-the-spot fines."

A spokesman for the National Census said: "We would never ever, in any circumstances, ask for on-the-spot fines.

"Fines are used only as a very last resort and, if this was to happen, it would involve the local magistrates court."

Although Census officials were chasing up unreturned forms, they would never ask for cash and always wore an identification badge, he said.

"It seems there are people who will take advantage of any situation to try to access people's homes make some money," the spokesman added. It appeared to be the first case in the country.

"Census enumerators will always operate from the doorstep and will not go inside a house unless specifically asked to."

Anyone who received demands to pay fines through the post should also ignore them and inform the police.

The suspect is described as being Asian, about 5ft tall, slim, with black hair and wearing a pink Asian-style dress and white scarf. Anyone recognising the description or with information about the offences should contact Bradford South CID on (01274) 376459.