Police are warning people to be wary of using money transfer services following the audacious scam.
The woman from Bradford received a telephone call to say she had won £50,000 but would need to make several payments via a money transfer service for her prize to be released.
She was then called by a man claiming to be a police officer who told her they were aware that she was being targeted by fraudsters and gave her a mobile number to ring should the man call again.
The woman then received another call, asking her to go to London to pay another £5,000.
When she said she could not get there the caller said he would send someone to her house to pick up the cash.
Believing that police were now involved, the woman handed over gold jewellery to the caller as she was unable to pay the requested amount.
Pc Toni Hinnells said: “This is a sophisticated scam, where a man has taken advantage of a vulnerable woman and defrauded her of thousands of pounds.
“We want people to be on their guard against this type of fraud and to only use money transfer services when absolutely certain who the recipient is, like a family member for example.
“If you don’t remember entering any prize draws or overseas lotteries or are asked to pay a fee up front to release a cash prize then it’s likely that you are being targeted by fraudsters and should contact Action Fraud on 0300 1232040.”