Japan’s ruling party has been accused of violating the Olympic charter after it failed to approve a bill to protect the rights of the LGBT community, during discussions marred by homophobic outbursts from conservative MPs.

Closed meetings held this month to discuss a bill, proposed by opposition parties, stating that discrimination against LGBT people “must not be tolerated” ended without agreement after some Liberal Democratic party (LDP) MPs said the rights of sexual minorities had “gone too far”.

A decision on a rival LDP proposal that calls on the government to “promote understanding” of LGBT people was postponed, according to Japanese media accounts of the meetings.

The failure to back a proposed law to protect LGBT rights was condemned by human rights groups, which said the party deserved a “gold medal for homophobia”, two months before Tokyo is due to host the delayed 2020 Olympics.

An unnamed lawmaker described LGBT people as “morally unacceptable”, while another MP, Kazuo Yana, said sexual minorities were “resisting the preservation of the species that occurs naturally in biological terms”, media reports said.

Eriko Yamatani, a former cabinet minister, told reporters after one discussion that transgender rights in other countries had enabled people born as men to “win lots of medals” competing against women, and to use women’s bathrooms.

“Given these absurdities, we should be a little more careful. Were it to grow into a social or political movement, wouldn’t there be consequences?” Yamatani, who opposes abortion and sex education in schools, was quoted as saying by the Mainichi newspaper.

Human Rights Watch accused the LDP of indulging in “ugly rhetoric” and noted that the Olympic charter bans “discrimination of any kind”.

“Japanese officials insulting LGBT people is not new, but it is increasingly out of touch with Japanese public opinion and the government’s place on the world stage,” the group said, calling on MPs to pass the equality act before the Tokyo Games open on 23 July.

Laurel Hubbard, a weightlifter from New Zealand, is set to make history this summer when she becomes the first transgender athlete to compete at an Olympics.

The MPs triggered criticism on social media and an online petition demanding that they withdraw the remarks.

One senior LDP official described Yana and Yamatani’s comments as “foolish”, while another who supports the proposed anti-discrimination law told the Mainichi that parts of the discussion had been “unbearable to listen to”.

Pride House Tokyo and the US-based campaign group Athlete Ally said in a statement: “These comments, if true, are in violation of the spirit of the Olympics and Paralympics, which Tokyo is hoping to host.”

The director of Pride House Tokyo, Gon Matsunaka, said: “How can athletes truly feel safe playing in a country where a member of the ruling party makes such discriminatory remarks?”

Japan is the only G7 nation not to fully recognise same-sex partnerships, but a recent court ruling raised hopes for a change in the law after it stated that not allowing gay couples to marry was unconstitutional.

Conservative LDP lawmakers have a history of insulting Japan’s LGBT community. In 2018, the lower house MP Mio Sugita said LGBT people were “unproductive” because they could not have children, and challenged the use of taxpayers’ money to support same-sex marriages.

Same-sex couples “don’t produce children”, she wrote in a magazine article. “In other words, they lack productivity and, therefore, do not contribute to the prosperity of the nation”.