The president of the British Board of Film Classification (BBFC), who is leaving his post at the end of the month, says the current system could be replaced by "advisory" certificates.
"In the very long term, all ratings will be advisory. It will all happen in a 10-year-period," he told the Independent on Sunday newspaper.
"To me, the BBFC's primary job should simply to be enable parents to regulate their children's viewing."
The board vets films and videos released in the UK, and Mr Whittam Smith's signature appears on a certificate before each production together with that of the BBFC's director, Robin Duval.
But its decisions on cinema releases can overruled by local authorities - recently, it passed Spider-Man with a 12 certificate, but some councils amended this to a PG rating for cinemas in their areas.
Relaxed regulations
The BBFC is already reported to be considering making the 12 certificate an "advisory" rating, like the US PG-13 certificate, which means under-13s can see a film if they are accompanied by an adult.
Whittam Smith, a former journalist who is best known for founding The Independent newspaper in 1986, said he felt the British public was happy with the way the system runs now.
During his time in charge he has seen film guidelines overhauled to protect children but also relaxed for adult viewers, allowing more graphic sex films to be rated.
"My guess is that 80 to 90 per cent of the population is happy with censorship laws as they are, while 10 per cent are for heavier regulation and 10 per cent are libertarians," he said.
"Those who want more just happen to be disproportionately represented by one incredibly powerful newspaper, the Daily Mail."
The 65-year-old is leaving the BBFC to become the Church of England's First Church Estates Commissioner, overseeing the management of church investments.