The director of the British Board of Film Classification has said the idea of harmonising film ratings across Europe is "impracticable".
Secretary received an 18 rating in Britain but a 12 rating in France
The EU is examining the prospect of applying the same film classifications across all its member states.
But BBFC director Robin Duval said harmonisation "may only be achievable by agreeing to abide by the standards of the most restrictive nations".
Many films have lower age restrictions in France than in Britain, he said.
Three-quarters of films currently receive a classification in Europe from U (universal) to 18.
But in the BBFC's annual report, outgoing director Robin Duval described the idea of applying a Europe-wide rating to each film as "an impracticable chimera".
What is regarded as acceptable for a film audience varies greatly between nations, he said.
"The British are almost alone in Europe, although not
in the world, to their sensitivity to bad language," Mr Duval said.
"The French place a much higher premium upon the cultural value of film than other nations when they classify."
For example Pulp Fiction, The Exorcist, Hannibal, Gangs of New York and Secretary were all rated 18 in Britain yet received a more lenient 12 rating in France.
Mr Duval added: "The Spanish tend to take a harder line than anyone on sexual immorality and the Scandinavians are most sensitive on violence and least on sex."
He said films may follow the example of video games, now regulated across most of Europe, in requiring liberal nations to abide by the ratings demanded by more conservative ones.
A BBFC spokeswoman said there were no immediate plans to introduce a harmonised ratings system but that the EU had not dismissed the idea.