Premier League clubs are leaving £1m's worth of sponsorship value on the table every game because of illegal streaming, according to the first study of its kind.

Commissioned by an unnamed Premier League club, the joint study was carried out by American sponsorship valuation firm GumGum Sports and London-based digital piracy experts MUSO.

Based on eight matches from last season, they found each match had an average illegal audience of 7.1 million viewers, with more than one million of those from China. The other big markets for digital piracy are Vietnam, Kenya, India and Nigeria, while the UK is 11th on the list.

In a statement, GumGum Sports vice president of partnerships and strategy Jeff Katz said: "Clubs and sponsors have never been able to quantify media exposure from unauthorised streaming, which over the years amounts to billions of dollars in unrealised value.

"Now we have a unique data set that gives an advantage to brand sponsors while also enabling clubs to better demonstrate the value they're driving on behalf of corporate partners."

The £1m per match figure is based on what the total audience - legal and illegal - would mean for pitch-side advertising and kit sponsorship income.

"Piracy audiences have too long been disregarded as offering no real value to rights holders and distributors, but the reality is that these huge audiences still see the same shirt sponsors and commercials as people watching the game via a licensed channel," said MUSO co-founder and chief executive Andy Chatterley.

"Sports rights owners are now waking up to the fact that they are leaving sponsorship money on the table by not measuring, understanding and gaining insight from the piracy audience."

While that is almost certainly true, it is also the case that digital piracy represents an existential threat to the current business model of most top professional sports, which have come to depend on big cheques from broadcasters for exclusive live content.