The BBC moved yesterday to protect one of its most valuable international brands amid claims that scenes shown on Sir David Attenborough's acclaimed series Frozen Planet were filmed in a Dutch animal park and not in the wild.

Eight million viewers saw images of a polar bear caring for her newly born cubs in scenes that were juxtaposed with pictures of the Arctic. The fact that the cubs were filmed in a man-made den in Holland was only revealed in an accompanying clip on the BBC's website.

"Beeb faked Frozen Planet" claimed a front page headline in yesterday's Daily Mirror, a story that was widely followed up. The paper quoted Sir David's commentary accompanying pictures of the cubs, in which he said: "But on these side slopes beneath the snow new lives are beginning. The cubs are born blind and tiny. An early birth is easier on the mother." On the BBC's website viewers marvelled at how the camera crew had apparently got so close to the new borns.

The allegations are potentially hugely damaging for the BBC, which licensed the most recent series of Frozen Planet to 30 networks around the world. Natural history brands have become crucial to the BBC's commercial arm, BBC Worldwide. The popularity of Frozen Planet has also been linked to a surge in interest in adventure holidays in the Arctic.

Yesterday Sir David went on ITV's This Morning to justify the way the footage was obtained. "It's not about patience; it's about safety," he said. "Safety of the polar bears and safety of the camera crew. If you had a camera in there, the mother may have killed the cub or the camera man."

In a further effort to limit the damage, the BBC argued that the television script had been written in a way that did not mislead viewers. "The commentary accompanying the sequence is carefully worded so it doesn't mislead the audience and the way the footage was captured is clearly explained on the programme website," said a spokeswoman.

The Independent was told that natural history viewers had told the BBC that they did not like the "flow" of programmes to be interrupted by details of where sequences were filmed and asked for such information to be given online. On the BBC website, the programme's producer, Kathryn Jeffs, explained that it would not have been possible to acquire pictures of the new-born cubs in the wild. "The problem for us is that they do it underneath the snow in these dens of ice," she said. "There is absolutely no way that we can get our cameras down there – it would just be completely impractical. Even if we could, we would not want to disturb the polar bears by getting that close. This was not part of the story that we could leave out of Frozen Planet."

But critics of the BBC's presentation of the footage claimed that the web clip was not easy to find and would not have been accessed by many television viewers. John Whittingdale, the chairman of the House of Commons on Culture, Media and Sport Committee, said the circumstances of filming should have been included in the commentary.

moving scenes the controversial sequence

"A female polar bear searches for shelter. Other bears are out on the frozen ocean looking for food but she won't feed again until next spring."

"Using as little energy as possible, she starts to build a shallow nest. The snow here is easy to work, it's soft and light ... and that is what she needs."

"Once the snow here is deep enough, she will dig down to make a den. She'll then lie, waiting for her cubs to be born."

"On these side slopes, beneath the snow, new lives are beginning. The cubs are born blind and tiny. An early birth is easier on the mother, who is barely awake."

"Her instinct to nurse is overwhelming. The cubs' plucking calls stimulate her to produce milk, and what milk: it's nine times richer than our own."

"In two more months, polar bear families will emerge on to the snowy slopes all round the Arctic. But for now they lie protected within their icy cocoons."

Was it right to give Mother Nature a helping hand?

Yes! says Gerard Gilbert, TV critic

Commenting in 2007 on the fakery scandal involving the Queen supposedly storming out of a portrait session with photographer Annie Leibovitz (a hoo-ha that cost the then-controller of BBC1 his job), the former head of ITN News-turned academic Stewart Purvis mentioned that "natural-history programme-makers have been doing it for years. You'll see footage of a lion chasing a deer, but the two animals were in fact filmed on different continents."

Yet that is not the average viewer's image of the BBC's flagship wildlife programmes, which have acquired an almost "national treasure" status. The current furore over the Frozen Planet polar bear birth scenes is fuelled by the high esteem in which wildlife film-making is held, and the secular sainthood bestowed upon its purveyor-in-chief, Sir David Attenborough. The suggestion that his immensely popular series are anything other than exactly as they seem has been taken as an affront to the viewing nation, no matter how impossible the shots in question would have been to obtain in the wild.

Perhaps we've just become too used to the omnipotence of the BBC Natural History Unit – of our belief in its ability to film anything anywhere. However, I sympathise with Sir David when he argues that explaining about the zoo in the commentary would have ruined the show's atmosphere. Programmes such as Frozen Planet rely on atmosphere (something Sir David is so adept at building) as much as any drama. Why transport us all the way to the Arctic only to yank us back to an animal park in the Netherlands?

There is an enormous amount of artifice involved in gathering any "natural" scene, and of persuading the viewer at home that they are alone in the wild. It might be more grown-up if we just accepted that instead of crying "Fake!" every time a scene is not exactly as implied.

No! says David Lister, Arts Editor

At this time of year we wouldn't want to be told that Father Christmas doesn't exist. Unhappily, we've been told the next worst thing. Sir David Attenborough, the voice and face of pure integrity, is accused of pulling a bit of a fast one.

If Sir David is Mr Honesty, the BBC is the repository of Reithian values, and natural history programmes are exempt from all the tricks and manipulation that bedevil so-called reality on the television screens.

Now all those tenets of faith risk being destroyed. The BBC has misled its viewers and has probably unfairly besmirched the name of David Attenborough in so doing.

Its excuses are risible. The proper explanation may well have been on the website, but I don't know anyone who watches a TV programme with their laptop on their knee, checking the programme website to be sure that they are not being misled. But thanks for the tip. I'll try to do that in future. It's one of the worst excuses I have ever heard from the BBC. And it sets a deeply worrying precedent. Is the message here really that programme-makers can play fast and loose provided that some sort of explanation is on the website, even if only a tiny percentage of viewers regularly peruse the website?

But equally disconcerting is the reasoning why they moved the Arctic to the Netherlands. There was a "safety" problem for the crew in filming the animals in their natural habitat.

Well, yes, but one of the most impressive aspects of the BBC's natural history programmes over the years has been the awe-inspiring risks that its film-makers take in getting up close and personal with wild animals. It was one area of life in which one hoped that health and safety did not rule.

So what happens now? Rename the programme Frozen Zoo? I hope that what happens is that the BBC realises and respects the trust in which it is held, and never practises this sort of deceit on its viewers again.