A Canadian man is being investigated after winning the lottery five times.

Seguro Ndabene - who has already won $1 million twice, $100,000 and $50,000 - scooped $17 million in January but his biggest win is now being disputed.

Ndabene's claim as sole winner is being questioned by a man who alleges the winning ticket was part of a group purchase and he wants a share.

According to court documents, Tony Koprnicky is the brother-in-law of the woman who runs the lottery kiosk where Ndabene purchased his winning ticket.

Koprnicky contacted the agency to say he had been a participant "in an open group-buying agreement that was being run by the lottery kiosk in the Airdrie Co-Op store."

Ndabene has insisted his win was just good fortune.