The makers of the Scottish film in competition at the Cannes Film Festival have attacked attempts by film bosses to give the bitter-sweet comedy The Angel's Share an 18 certificate because of its "very strong language".

Speaking at the festival yesterday, Ken Loach, the film's Scottish writer Paul Laverty and its producer Rebecca O'Brien criticised the initial move by the British Board of Film Classification (BBFC ) to give the Glasgow-shot film the adult rating purely because of its robust colloquial language.

Ms O'Brien said the 18 rating for its language was "offensive" and an attempt at "censorship".

"In the UK we have had to make changes to the language to get the language a 15 certificate, we have had to move some words from the version seen here in Cannes," she said.

"We have made films with heavy scenes of torture, with waterboarding and fingernails being torn out, and they have been 15, but the BBFC was going to give The Angel's Share an 18 certificate for that.

"The language in the film is the way people speak, it's completely natural and I think the language of middle England, that the BBFC represents, is somewhat different.

"If they are looking for diversity in film they should look at this film and Glasgow and see that there are different ways of speaking and that should be acceptable to all and not be censored."

A statement from the BBFC said: "[The] Company chose to reduce the number of uses of very strong language in order to obtain a 15 classification.

"An uncut 18 classification was available."

The use of one strong word in particular was the main issue, particularly when used in an aggressive way, Ms O'Brien said, adding that the film had not been cut but had certain words obscured.

Mr Loach said they could only use the word seven times.

"Only two of them could be aggressive. It gets into the realms of surrealism here in terms of language," he added.

"The British middle class is obsessed with what is called 'bad language', but of course bad language is manipulative language, and they are happy with that, but the odd oath, a word that goes back to Chaucer's time, they ask to cut.

"I think we should have respect for our ancient oaths and swearwords."

Mr Laverty said: "This is an issue of tremendous hypocrisy."

At the screening of the film in Cannes, it was given English subtitles, to help the audience understand what the Scottish characters were saying.

However, it will not be released in the UK, in June, with subtitles.

Mr Loach said: "Of course when it is released in the UK it won't have subtitles, but they were for the benefit of those for whom English was not their first language. We did fight the idea quite hard, because it is perfectly comprehensible."

Ms O'Brien said: "We are also trying to sell the film to other countries and so if English is not their first language then it is much easier to sell.

"We haven't sold it to America yet and hopefully it will be in all its glory."

Mr Laverty added: "If someone genuinely just cannot catch it and this helps them understand it, I have no problem with it. I think it is better than someone trying to dilute their language or have some kind of mid-American accent to suit the US. I would be against that."

Paul Brannigan, who stars as Robbie in the film, said the unemployed character he plays was like thousands of young people in Glasgow.

He said even after starring in the film, and a role with Scarlett Johansson in Under The Skin, he was looking at a period of unemployment. "After this I am trying to evolve my career, continue some football coaching and my volunteer work in the community," he said.

The Angel's Share was shot in Scotland with a Scottish cast but did not receive money from Creative Scotland, the arts funding body that houses the film funding responsibilities of the former Scottish Screen. Instead it received backing from bodies in France, Belgium and Italy.