Media playback is unsupported on your device Media caption Ken Loach: "Public money should go to fund a wide variety of projects"

The British film industry should back more mainstream movies, a report is expected to recommend next week.

Ahead of a visit to Pinewood Studios on Wednesday, Prime Minister David Cameron said the film industry should support "commercially successful pictures".

His comments come before the publication of Lord Smith's review into the government's film policy on Monday.

The review was commissioned to find out how the industry could offer better support to UK film-making.

Mr Cameron praised the UK film industry but said "we should aim even higher, building on the incredible success of recent years".

He acknowledged the British film industry had made "a £4bn contribution to the UK economy and an incalculable contribution to our culture".

Lord Smith, the former Labour culture secretary, is also expected to recommend developing an export strategy to increase the profits of British films.

Speaking to the BBC, director Ken Loach said it was important to have a diverse film industry with a wide range of films to choose from.

"If everyone knew what would be successful before it was made, there would be no problem," he said.

Media playback is unsupported on your device Media caption Tom Hiddleston: "There are no hard and fast rules for success"

"What you need to do is fund a lot of different, varied projects and then you'll get a really vibrant industry."

Loach added he would encourage more independent cinemas, saying: "The market does not provide choice if you don't intervene."

Oscar-winning screenwriter Julian Fellowes, who was a member of Lord Smith's panel, said it was necessary to support mainstream films.

"There has been the thinking in the past that public money should only go into films that can't get any investment anywhere else," he told Sky.

"When you actually analyse that it means it should only go into films that nobody could conceivably want to see and there's no logic in that - you want to make a film-friendly, audience-friendly industry.

"It's not a question of not having minority films, it's just opening it up so we're also getting behind films that people might want to see."

Grassroots support

Mark Herbert, chief executive of Warp Films, which has made films including This Is England, Submarine and Tyrannosaur, said it was impossible to predict which films would be commercially successful.

He said the company's biggest commercial success had been Four Lions, a comedy about inept suicide bombers.

"It took £3m at the box office, won festivals, did brilliant business in Germany and France and is up there with big studio films in terms of DVD sales.

Image caption Adam Deacon wrote, directed and starred in the comedy Anuvahood

"Yet nobody backed that. There was no public money in that. When I was trying to raise the money, I had very experienced funders and producers saying 'Nobody will go and watch this film.'"

He also pointed out that black and white silent film The Artist was making more money per screen than any other film currently on release in the UK and is favourite to win best picture at the Oscars - but would not have looked like a hit on paper.

"You can imagine people saying 'Who's going to watch a black and white silent film?' But they are, and people are loving it," he said.

Mr Herbert added that independent regional film-makers must continue to be supported as well as major film studios, and that new talent must be nurtured by supporting low-key, low-budget films.

"For talent to get to the stage where they can pull off [making] a blockbuster, they need to support the grassroots. It's like having an elite England football team and not supporting any young players."

Speaking at the announcement of this year's Bafta rising star shortlist, nominee Adam Deacon, who wrote, directed and starred in Anuvahood said: "2011 was a great year and our films like Attack the Block and The Inbetweeners were competing against America.

"It shouldn't all be about The King's Speech and these sort of films. We need fresh talent and fresh ideas."

Image caption The Inbetweeners earned more than £45m at the box office

Film critic Mark Kermode, at the same Bafta event, said it was "impossible" to judge what was going to be a commercially successful film.

He said that independent cinemas and adventurous programming were an important factor.

"There are loads of great British films made every year and only a fraction of them actually find a foothold in cinemas. If you really want to address the way the British film industry works address exhibition and distribution - that's the answer."

The British Film Commission welcomed the prime minister's recognition of the economic impact of the movie industry.

Chairman Iain Smith said: "It is reassuring to hear the Government understands the role big budget, international movies shooting in the UK plays in building a world-class skilled workforce, while boosting the UK economy."

The report follows the abolition of the UK Film Council last year, which handed over its funding responsibilities to the British Film Institute (BFI).