Anti-monarchy group Republic has called on the BBC to release the 1969 documentary "Royal Family".
The film hasn't been broadcast since the 1970s. This week it was posted on YouTube before being removed on copyright grounds.
Republic, which campaigns for the abolition of the monarchy, has said it is outrageous that the BBC is helping the royals protect their own image.
Speaking for the campaign, Graham Smith called on the BBC to release the documentary, saying:
"This film should be in the public domain so that people can make their own judgements about the royals."
"There is a clear public interest in its release, and there is clearly something wrong with the BBC taking instructions from the royals."
"The BBC produced the film yet it is claimed to be covered by Crown copyright. The BBC defends its impartial news reporting yet has allowed the subjects of a documentary to control access to it."
"It is clear that the royals are worried about damage to their image, which is why they're insisting the documentary stay locked away. It is not the job of the BBC to protect the royals from scrutiny. No-one else would have that kind of power over the BBC."
"This is a BBC documentary, the decision to broadcast it or make it available online is the BBC's. To deliberately keep it away from the public is an outrage."
"It's been claimed that at the time David Attenborough warned that the film was in danger of "killing the monarchy". And then the film was locked away, never to be seen again. That is a disgraceful way for the BBC to behave."
"Having seen the documentary I can say it doesn't paint the royals in a good light. That's something the public have a right to see, and people will make up their own minds about who the royals are today."
Republic will be writing to the Director General of the BBC to set out the case for releasing the documentary.
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