The threat emerged as The News reported yesterday how a family from Portsmouth had been conned out of £716 by an African gang, with the false promise of a puppy being delivered.

The Dunkley family were hit by the scammers when daughter Chalsea selected a cute poodle puppy from an online advert.

The 16-year-old e-mailed the owner, who claimed to be living in Scotland and was selling the puppy because a new landlord did not allow dogs.

The supposedly 12-week, three pound Paddy was to be couriered to the family's home in Swanmore Road, Havant, for a £150 fee, using an agency called Express Pet Delivery

Bizarrely, the family were told to pay the money to the company's HQ in Douala in Cameroon via MoneyGram – but after doing so, they were hit with a slew of additional e-mails and even phone calls from an African man, demanding extra payments for the safe arrival of the dog, claiming that it needed to be insured for travel and given an additional injection.

Terry Dunkley, 41, said the dog was mainly intended as a gift for his sick wife, for whom he is a full-time carer, because she was allergic and they could only have certain breeds. But the second time an additional payment was demanded, the penny dropped.

'I've reported it to the police but they said there's nothing they can do, they can't investigate it,' he said.

'We didn't think because we were excited. We'd had a Yorkie and lost it in November, and just wanted another dog. My wife's birthday was coming up, and we thought it was being delivered for that. But it was when they just kept asking for more money that it dawned on me.'

In Cameroon, where the average income is around just $2,000 per year, the scammers have made a very tidy profit from the trusting Dunkleys.

Zorica Lys, principal trading standards officer for Portsmouth, said they had little chance of recovering the family's cash.

She said: 'It's quite obviously a scam. There are quite a number of blogs online talking about this.

'Quite often scams like this now are using Western Union or MoneyGram, which are legitimate companies.

'Until quite recently you would have been asked for your bank details, but the banks have wised up a lot to this.'

She advised people buying pets not to purchase online, and to go to shelters such as the RSPCA, where you can often pick up animals for free.