Mulvaney identifies as a trans woman but has not undergone transition surgery, and her Instagram post to her 1.8 million followers on Wednesday (April 5) promoting a new Nike sports bra and leggings for women was under a "paid partnership" banner.

The post has been liked nearly 380,000 times.

Mulvaney had earlier shared a video promoting the Bud Light beer.

Former British swimmer and Moscow 1980 women's 400 metres individual medley Olympic silver medallist Davies has urged people to shun Nike.

"Women are not a parody, caricature or stereotype companies, and those of you disrespectful enough to not understand that will lose customers," she wrote on Twitter.

"We will make our voices heard through our spending power and boycott companies that don’t know what a woman is."

Davies has long been a vocal campaigner against the inclusion of transgender athletes in women's sport on the grounds of fairness, insisting they have an unfair advantage.

She has doubled down on her calls to boycott Nike, and criticised inequality in sponsorships for female athletes in the United States.

"Women get one per cent of the USA sports sponsorship cash," Davies said on Twitter.

"Let that figure really sink in.

"In a world where they represent 51 per cent of the population.

"And we’re supposed to be happy males now get to advertise our sports bras - just say no."

Montreal 1976 Olympic decathlon champion Caitlyn Jenner of the US has also criticised Nike for its partnership with Mulvaney.

Jenner came out as a trans woman in April 2015, but has opposed the participation of trans athletes in women's sport.

"As someone that grew up in awe of what [Nike co-founder] Phil Knight did, it is a shame to see such an iconic American company go so woke," she said on Twitter.

"We can be inclusive but not at the expense of the mass majority of people, and have some decency while being inclusive.

"This is an outrage."

Nike has previously partnered with the first trans woman to play in Argentina's professional football league Mara Gómez as part of its "play new" campaign, describing her as "changing the rules, generating new opportunities, leaving discrimination behind".

It has urged respect on social media, after the controversy over its Mulvaney partnership.

"You are an essential component to the success of your community," Nike said.

"We welcome comments that contribute to a positive and constructive discussion.

"Be kind.

"Be inclusive.

"Encourage each other.

"Hate speech, bullying, or other behaviours that are not in the spirit of a diverse and inclusive community will be deleted."

Mulvaney received numerous transphobic comments and abuse on her original post, and has since written on TikTok: "Thank you all for making me feel supported, I am not alone."

The US-based Gay and Lesbian Alliance Against Defamation dismissed criticism of brands for using trans influencers.

"Including our community in marketing is nothing new, but what is new is the extreme right-wing politicisation of a company’s creative and business decisions," its President Sarah Kate Ellis told Time magazine.

"Companies will not end the standard business practice of including diverse people in ads and marketing because a small number of loud, fringe of anti-LGBTQ activists make noise on social media."

The debate on transgender athletes' participation in women's sport has become increasingly polarised.

In November 2021, the International Olympic Committee approved new guidelines which granted increased flexibility to International Federations to set their own policy, with President Thomas Bach insisting there cannot be a "one-size-fits-all" approach".

In June last year, the International Swimming Federation - now World Aquatics - took the decision to severely restrict the participation of transgender athletes in women's events.

World Athletics last month banned transgender athletes from its women's competitions.

Critics have argued these policies are discriminatory, but supporters say they safeguard fairness in women's sport.