Paul F. DeMeester first threatened legal action back in 2017, when he accused the International Association of Athletics Federations (IAAF) of discriminating against women by not including a race for them at major championships.

A race was part of the 2017 World Championships programme in London amid legal pressure from DeMeester and former Australian athlete Tim Erickson, but only seven athletes took part and the discipline is not set to feature at Tokyo 2020.

The IAAF’s Race Walking Committee has previously said the quality of the women’s event must improve before it can be considered for Olympic inclusion but DeMeester, along with several athletes, are launching a legal challenge against both the IAAF and International Olympic Committee (IOC), saying to include a race for men but not women is discriminatory.

In a statement DeMeester, who successfully lobbied against an IAAF plan to cut the men’s 50km race from Tokyo, said the Olympic Charter’s position on gender equality that any form of discrimination on the grounds of gender is “incompatible” with the Olympic Movement, means a women’s 50km race should have featured in every Games since Beijing 2008.

“Obviously that did not happen, rendering all those lofty constitutional and fundamental Olympic principles of gender equality and the prohibition against gender discrimination as mere empty words,” DeMeester said.

The release continues that female race walkers have “proven their worth” over 50km, highlighting that the difference between the men’s and women’s world records is similar in percentage terms to the difference in the marathon – an event which has consistently featured both men and women in the Olympics since 1984.

“The lawsuit will seek to have women race walkers included in the Tokyo 2020 Olympic 50km race walk event,” it reads.

“We are not seeking a new event,” DeMeester said, adding they would like to see women complete the course alongside the men, merely with separate classifications.

“That’s one small step for the IOC and IAAF but one giant leap for gender equality.”

Athletes to have backed the legal challenge include European and world champion over 50km Ines Henriques, Australian champion Claire Woods, Ecuadorians Paola Perez, Johana Ordonez and Magaly Bonilla plus Spain's Ainhoa Pinedo.

One male athlete, New Zealand’s Quentin Rew, has also reportedly backed the case, with DeMeester’s press release saying the two-time Olympian “feels strongly that women athletes should have the same opportunities as men.”

Two years ago, the chair of the IAAF’s Race Walking Committee, Maurizio Damilano, said they considered gender equality to be “very important” but suggested the priority in this case is improving the standard of women’s racing over 50km before including it at major events.

"We are very happy to have men and women in all disciplines,” the men's Olympic 20km champion at Moscow 1980 said.

"We need to defend race-walking in athletics – but we need quality.”

The IOC initially wanted to cut the men’s 50km race from Tokyo 2020 in favour of a mixed relay to ensure a more gender-equal programme, but the schedule was rejected in April 2017.

In a statement sent to insidethegames, a spokesperson for the IAAF said they had tried to get a women's event included in the 2020 Games.

“The IAAF requested the inclusion of the 50km women’s race walk in the event programme for Tokyo 2020 following discussion by the IAAF Competition Commission and Council in December last year," they said.

"The IOC has restated in its response that the IOC Executive Board finalised the Tokyo 2020 event programme in June 2017. 

"This was before the 50km women’s race walk was included at the IAAF World Championships in London in 2017. 

"We continue to discuss race walk events with the IOC ahead of finalising the Paris 2024 Olympic Games programme."

However, in a further development, under plans recently approved by the IAAF Council, the 50km race walking event may cease to exist after Tokyo 2020.

Last month the IAAF Council approved plans “in principle”, to reduce the 50km distance to 30km after the next Olympics in an attempt to improve the sport’s appeal among younger audiences.

The plans would also see the 20km distance halved, another move that has received criticism.

Among those against the new plans are Britain's Commonwealth Games silver medallist Tom Bosworth and Canada's Evan Dunfee, fourth in the 2016 Olympic 50km race walk.

Others to have put their protest on record include Australia's London 2012 50km champion Jared Tallent, Rio 2016 50km champion Matej Tóth of Slovakia, France's world 50km record holder and champion Yohann Diniz and Portugal’s Henriquez, the women’s 50km world champion.

It is claimed the proposals "reflect the reality" that the event programme across all major athletics meetings and events will become shorter and more dynamic, but many athletes have criticised the decision to shorten the traditional distances.

"Athletes often times struggle to know when the right time to retire is,” Canada’s 2015 Pan American Games 20km gold medallist Evan Dunfee tweeted.

"So thank you IAAF for giving me a clear timeline to know exactly when to evacuate this sinking ship.

"It is sad though.

"2024 was going to be my peak.

"Maybe I can learn to cross country ski or take up ultra running, be a part of a community that still appreciates endurance."

In response to DeMeester's legal challenge, in a brief statement sent to insidethegames the IOC simply reiterated that the sports programme for Tokyo 2020 has already been decided. 

"Following the Olympic Charter, the IOC Executive Board finalised the Tokyo 2020 event programme in June 2017, three years prior the Olympic Games," they said.