Under the plans, films could be interrupted once every 30 minutes, rather than the present 45 minutes.
The rule which requires a 20-minute space between advertising breaks within other types of programmes would be scrapped.
Ofcom is also seeking views on whether rules banning advertising during royal ceremonies and live parliamentary proceedings should go.
Under the proposals, there would be an end to the rules which forbid advertising breaks in religious programmes or documentaries that last less than half an hour.
The regulator believes the current rules need to be updated to cater for a multichannel, digital era, and the threat to TV advertising from the internet.
Ofcom said: "Many of the restrictions on advertising in particular kinds of programme (eg documentaries with a religious theme) reflect the social attitudes prevailing more than 60 years ago.
"Because these rules make it less profitable to show these programmes, particularly during peak viewing hours, they may even discourage broadcasters from making or acquiring such programmes." It added: "Over the past few years, the cost of advertising time on television has fallen."