Film-makers who abuse the system of tax breaks for British films are facing a crackdown by the UK Government.
The Pianist was a co-production. There is no suggestion that it abused the system.
Films that are British or co-produced by Britain get tax relief in the UK.
But the government suspects some co-productions of falsely claiming to spend more in the UK to qualify, while others do not give value for money.
Arts Minister Estelle Morris launched a review on Tuesday, saying she was "determined to ensure the right people are reaping the benefits".
The UK has co-production treaties with more than 30 countries, meaning some jointly-made films can be officially recognised as British - and qualify for tax breaks.
The review will be carried out by the Department for Culture, Media and Sport together with the UK Film Council, which funds and promotes British film.
Dogville (above) - UK, US, Denmark, Sweden, France, Norway, Netherlands, Finland, Germany, Italy, Japan
The Pianist - UK, France, Germany, Netherlands, Poland
Underworld - UK, US, Germany, Hungary
Sweet Sixteen - UK, Germany, Spain
New guidelines were also published to tighten the rules.
"Co-production is central to the future of the British film industry and the UK can lead the way," she said.
"But it is a two-way deal. Co-productions and the associated tax breaks must lead to more jobs in film in this country and more work for our film making facilities."
The number of British co-productions made has risen from 10 in 1992 to 142 in 2002.
An example of a successful co-production - which is not suspected of abusing the system - is the Oscar-winning drama The Pianist.
Other recent co-productions include Underworld, starring Kate Beckinsale, Dogville, with Nicole Kidman, and Ken Loach's Sweet Sixteen.
A spokesman for the Department for Culture, Media and Sport would not name any films suspected of fiddling the system.
Films qualify as British if either 70% of the budget is spent in the UK, or if there is a co-production agreement with another country.
Countries that have treaties with the UK include Australia, Canada, France, Germany, and New Zealand.
Ms Morris also said the amount spent in the UK from UK/Canada co-productions must double to qualify as a British movie.
A total of 40% of the budget must be spent in Britain, up from 20%.