UIPM vice-president Vyacheslav Aminov had told Russian state-owned news agency RIA Novosti that the new discipline could be trialled at the season-opening World Cup in Cairo next month, but Pentathlon United tweeted that it had been informed by the Athletes Committee that there were no such plans.

The pressure group asked: "What is going on?

"Does anyone know what is going on?

"Athletes' careers are on the line.

"This is simply not good enough from the UIPM."

The UIPM Athletes Committee revealed on Instagram last month that eight potential alternatives to riding, including pillow fighting, were discussed at an "Athlete Focus Group".

However, participants in the UIPM's Working Group tasked with overseeing the process to find a replacement fifth sport are believed to have signed non-disclosure agreements (NDAs), and few details have emerged from the meeting last month in which its first proposals were presented.

Pentathlon United argues that athletes have been left in the lurch, and raised practical issues associated with testing a fifth discipline.

"When and where will these tests occur?

"And who is going expected to take part?

"Athletes need time to prepare.

"And the insurance covers athletes to compete at modern pentathlon, not some unknown sixth sport.

"Athletes cannot be expected to take part."

Pentathlon United was established following the controversial decision to axe the equestrian element of the sport at the Olympics from after Paris 2024, and has been a vocal critic of the process which led to that decision.

It has called for the Executive Board, including long-serving President Klaus Schormann, to step down.

The search for a new discipline comes when the sport is already undergoing major change, with a 90-minute competition featuring an elimination system set to be used at Paris 2024, replacing the two-day format used at Tokyo 2020.

One of Pentathlon United's most prominent members - Britain's Sydney 2000 Olympic bronze medallist Kate Allenby - told insidethegames that the uncertainty is putting athletes' reputations at risk.

"We've already had the 90-minute format forced through by force majeure, which is a monumental change from the Tokyo format," Allenby said.

"That format's going to be in place during qualification for Paris, and since then we've had the equestrian discipline removed by force majeure.

"Athletes need time to prepare.

"The modern athlete has financial value, and reputational credibility is at stake.

"It's about making sure that the athletes are front and centre of this process.

"It seems like they are, but they're not."

Allenby added that she has concerns over the signing of NDAs by members of the UIPM's working group assessing the fifth discipline, believing that they risk excluding athletes from the process.

"There’s no place for NDAs here," Allenby insisted.

"The IOC [International Olympic Committee] made it very clear this has to be an athlete-driven process.

"The signing of NDAs makes it impossible for the athlete community to have full transparent access and involvement in this critical process.

"The UIPM must immediately release the athletes from the NDA so they can properly consult and engage with the athletes on any discussions taking place.

"If they don’t do this then any decisions will simply look like a pre-determined stitch-up and won't have the confidence of the athletes."

Riding was dropped by the UIPM after Germany's coach Kim Raisner was sent home in disgrace for punching a horse in the women's competition at Tokyo 2020.

Modern pentathlon has been left off the initial programme for Los Angeles 2028 by the IOC, with a deadline of 2023 set for the UIPM to address concerns.

IOC President Thomas Bach has warned that the UIPM must finalise its proposal for the replacement for riding and for the overall competition format before the sport can be included.

This, Bach insisted, must "demonstrate a significant reduction in cost and complexity, and improvement across the areas of safety, accessibility, universality, appeal for youth and general public".

However, numerous athletes and National Federations have condemned the decision to remove riding, and Allenby argued that equestrian is worthy of its place in modern pentathlon.

"Athletes want high-class sport that is safe and credible," Allenby said.

"So far we have heard nothing that satisfies that more than our equestrian discipline.

"Imagine if they’d spent this much time and effort developing our equestrian sport."

UIPM secretary general Shiny Fang has asked for proposals on the new discipline to be submitted by Tuesday (February 15)

The governing body has claimed that the new discipline is aimed at reducing the sport's cost and complexities and making it "more accessible to the global community".