An AFL punter has placed a whopping $500,000 with Sportsbet on St Kilda to win the 2010 premiership at $6.

Sportsbet are claiming it is the biggest bet and potentially the biggest collect in AFL history.

The Saints were paying $3.60 for the premiership less than a month ago but their price went out to $6 after bad losses to Collingwood and Essendon over the last three weeks.

St Kilda's price has now shortened to $5 after Thursday's big punt.

"Clearly this punter thought the price was too good to refuse - he has had an account with us since April but this is the first bet he's placed," a Sportsbet spokesman said.

The largest bet Sportsbet had previously taken on the 2010 premiership was $50,000 in March on the Western Bulldogs at $6.50.

Geelong remain the flag favourites with Sportsbet at $3, while Collingwood have eased slightly to $3.60.

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