Lottery bosses have warned they will take action against people who attempt to fraudulently claim a £33m jackpot.
Hundreds of people have come forward claiming their ticket was lost, damaged or stolen, including a woman who said she washed her ticket by accident.
Half of the record £66m Lotto jackpot from 9 January has not been claimed, but the winning ticket - with the numbers 26, 27, 46, 47, 52 and 58 - was bought in Worcester, Camelot said.
Camelot is investigating all claims.
A spokeswoman said: "With prizes of this size, it's perfectly normal to receive lots of claims from people who genuinely think that they may have mislaid or thrown away what they believe was the winning ticket.
"However, if we believe that somebody has intentionally attempted to defraud the National Lottery, then, just like any other company, we reserve the right to take whatever action we consider is appropriate."
Shula de Jersey, a criminal lawyer at firm Slater and Gordon, said an intentional attempt to make a fake claim could be deemed "fraud by false representation", a criminal offence under section two of the Fraud Act.
The extent to which it could be deemed an offence or prosecuted would depend partly on the extent to which an individual went to fake a claim - for example by falsifying a ticket - she said.
On Saturday, a woman in Worcester, identified in newspaper reports as grandmother Susanne Hinte, claimed she had the winning ticket, but had put it through the wash in the pocket of a pair of jeans.
Natu Patel, who runs Ambleside News in Warndon, Worcester, where the woman made her claim, said the ticket bore the winning numbers, but the date and barcode were illegible.
A lot of people had been in touch since, which had been "very exciting, and worrying as well", he said.
His wife said one woman tried to claim Mrs Patel had sold her the winning ticket - but Mrs Patel was in India at the time.
Another woman rang the shop to claim her son had bought the ticket from their shop, but lost it, she added.
"I said, you tell Camelot, not me!" she said.
Under the terms of its licence, Camelot has discretion to pay prizes in respect of stolen, lost or destroyed tickets if a player has submitted a claim in writing within 30 days of the draw.
If the player could provide sufficient evidence, Camelot would investigate and determine "at its discretion whether the claim is valid, and is able to pay the prize 180 days after the draw", a spokeswoman said.
If the Worcester prize goes unclaimed after a deadline of July 7, the money will be donated to good causes, the lottery operator added.
Camelot said it had not released details of the shop where the winning ticket was bought and no retailer had been informed that they sold the winning ticket.
A spokeswoman said: "We would only release details of the shop if we received a valid claim and the ticket-holder subsequently took publicity. We still would urge all players to check their tickets and contact us if they think they have the winning one."
Married couple David and Carol Martin, both 54, from Hawick in the Scottish Borders, won the other half of the £66 million jackpot, the UK's biggest ever Lotto prize.