Almost $1.5bn (£1.1bn) has been wiped off the value of the exercise bike firm Peloton after a backlash against a Christmas advert widely derided as “sexist and dystopian”.

The advert, which has been viewed almost 2m times on YouTube, shows a woman receiving an exercise bike from her partner on Christmas morning. The gift inspires her to record a video diary of her exercise sessions, in which she proudly says: “A year ago I didn’t realise how much this would change me.”

The 30-second advert – titled “The gift that gives back” – was first released in mid-November, but this week a storm of criticism gathered pace online, and even inspired a series of spoof video remakes.

Critics called it “offensive” and “dumb”, pointing out that the woman was already slim at the start and the implication that her partner thinks she needs to get fitter and lose weight was patronising and damaging.

The backlash against the business – which sells £2,000 bikes equipped with screens for virtual spin classes and has an army of celebrity fans including David Beckham and Hugh Jackman – has reached such a pitch that $1.5bn has been wiped off its value, which had reached $9.39bn before the advert. On Tuesday its shares fell 9%, and by lunchtime on Wednesday the shares were down another 6%.

Ash Bendelow, the managing director of the UK creative agency Brave, described the advert as “cringe, old-fashioned and tone deaf”. He added: “It reminds us of the ‘seven tips for keeping your man’ notions from the 1950s, rather than where society is today in 2019.”

The advert has even been compared to Charlie Brooker’s dystopian television series Black Mirror, not least because the woman’s grateful thank you to her partner at the end is delivered when she shows him the vlog clips, on what appears to be Christmas the following year.

Others suggested that at times it resembles a hostage video.

On YouTube the video is still gaining thousands of views every hour, but was attracting five “thumbs down” ratings for each “thumbs up”. Peloton turned off comments on the YouTube post.

Other social media responses have been more graphic.

Peloton, which also sells treadmills, aims to become the “Netflix of fitness”. “On the most basic level, Peloton sells happiness,” the company said this year.

It styles itself not as a mere provider of exercise bikes but as a company that has “the opportunity to create one of the most innovative global technology platforms of our time”.

Its flagship product is a £2,000 stationary bike with touchscreen. Users can stream or download fitness classes for a monthly fee – £39 a month in the UK – which allows them to interact with instructors or other members, without having to leave home. They can even digitally “high five” other riders.

The New York-based company was founded in 2012 by John Foley, a former executive at the book chain Barnes & Noble. When the company floated on the US stock market in September it was valued at $8bn, even though it was loss-making.

It launched in the UK last year and has since opened nine showrooms where potential customers can try out the equipment. Peloton had sold 577,000 of its hi-tech bikes and treadmills by the end of June this year, but believes it can go on to sell 14m in the US, UK, Germany and Canada.

In the UK, the Advertising Standards Authority (ASA) introduced new rules in January under which adverts “must not include gender stereotypes that are likely to cause harm, or serious or widespread offence”.

In August Philadelphia cream cheese and Volkswagen became the first brands to have adverts banned under the guidance after complaints from the public that they perpetuated harmful stereotypes. The campaign for Philadelphia featured new fathers acting ineptly while looking after their children, while the VW advert for its electric e-Golf vehicle showed a woman sitting on a bench next to a pram.

While the Peloton advert has prompted outrage on social media, Geraint Lloyd-Taylor, a partner at the law firm Lewis Silkin, said it did not breach the ASA rules. However, he added: “The ad doesn’t seem to advance the cause of gender equality.”

In a statement to CNBC, Peloton said it was disappointed by how some people had misinterpreted the advert, but was “encouraged by – and grateful for – the outpouring of support we’ve received from those who understand what we were trying to communicate”.

It added: “We constantly hear from our members how their lives have been meaningfully and positively impacted after purchasing or being gifted a Peloton bike or Tread … Our holiday spot was created to celebrate that fitness and wellness journey.”

Bendelow said the reaction seemed excessive, and it may still boost sales: “The outrage is perhaps a little disproportionate and only time will tell whether there will be many Pelotons underneath the Christmas tree.”

The ASA told the Guardian it had so far received just one official objection to the advert. But the complainant did not take issue with the advert’s apparently sexist tone: their problem was that the woman featured appeared to be cycling faster than humanly possible.

• This article was updated on 6 December 2019 to include the figure for Peloton’s stock-market value just before the advert, $9.39bn.