Hobart man lost $250,000 in cold call scam

An elderly Hobart man who lost $250,000 is one of the victims of cold call scams that has prompted a national warning.

Invitations to take part often come via email, letter, phone or as a pop-up while browsing the internet.

Tasmania Police Sergeant Gen Hickman said on Monday that if the deal sounds too good to be true, it probably is.

"The scammers make money by keeping the funds you have invested or provided, or by boosting the price of stock in a company they already have shares in, they sell their shares and make a huge profit and leave you with a loss," she said.

The 77-year-old Hobart man invested with an overseas binary options broker whose company was eventually liquidated.

The Australian Criminal Intelligence Commission, the Australian Securities and Investment Commission and police joined forces on Monday to issue a warning on the scams, which are fleecing Australian investors of an estimated $50 million each year.