The film, produced by the Church of England initiative JustPray.uk, received clearance from the British Board of Film Classification and the Cinema Advertising Authority, but Digital Cinema Media (DCM) has refused to show it.
That's despite the Church claiming DCM offered them a discount rate just weeks before.
Asked for the PM's response to the ban, a Downing Street spokesman told a regular Westminster media briefing: "He thinks it is ridiculous."
The spokesman declined to expand on the rationale behind the PM's view or to say whether Mr Cameron thought the decision should be reversed.
DCM has defended its decision in the face of mounting criticism, saying some ads could cause offence to people of different faiths, political persuasions or those of no faith.
In a statement, DCM said: "DCM has a policy of not accepting 'political or religious advertising' content for use in its cinemas.
"Some advertisements - unintentionally or otherwise - could cause offence to those of differing political persuasions, as well as to those of differing faiths and indeed of no faith.
"In this regard, DCM treats all political or religious beliefs equally."
Archbishop of Canterbury Justin Welby, who features in the ad said it is "extraordinary" that Britain's biggest cinema chains have banned the advertisement.
Several MPs have jumped to the defence of the ad, including Mayor of London Boris Johnson.
Tweeting a response in a Q&A session, he said the ban was outrageous and expected a u-turn.
Christian Labour MP David Lammy also tweeted his shock:
Cinema chains banning an ad that features The Lords Prayer beyond belief. Surely we are bigger than this. #JustPray— David Lammy (@DavidLammy) November 22, 2015
He told Premier's News Hour why he thinks the three cinema chains shunned the advert: "Because we're living in aggresively secular times, and frankly people would rather pray at the altar of consumerism than express spirituality, which in the end is what the Lord's Prayer is about.
"We have an established church. Now if we want to get rid of the Church of England... the Queen no longer the head, then let's go ahead and do that, but let's at least have that discussion first.
"At the moment we do have that established Church which means we come together as a nation [under Christianity]. We've just had Remembrance Sunday!
"I think this is more than a rights agenda. I think this is about the very nature of our country, and erasing a fundamental aspect of the kind of country I want my children certainly to grow up in.
"Write in. Complain. Bombard the cinema chains, bombard the Secretary of State. Write to your MP. Say that you're upset about this. Join the petitions."
Listen to Premier's Hannah Tooley speaking to David Lammy MP on the News Hour: