The Paralympic Games were facing a fight for credibility last night after five nations, including Great Britain, sent a letter to Alan Dickson, the president of the Cerebral Palsy International Sports & Recreation Association (CPISRA), which questions the basis of the disability classification in seven-a-side football.

The Timeshas received a copy of the letter signed by Ukraine, Brazil, Great Britain, Holland and Ireland, who reacted after one of the Ireland players, Derek Malone, was ruled ineligible because CPISRA decided that, although he has cerebral palsy, he does not meet the minimum disability criteria.

“We the undersigned . . . believe that classification process is not open and transparent,” the letter read. “Players’ classes are changed too often and without any traceable criteria. All decision-making is monopolised by a single person, the chief classifier, ruling the sport [when he is] not even a football technician. It is frightening to know that CPISRA is about to implement a new classification system without consulting any member nations.”

The nations demanded clarification of two cases. The ineligibility of Malone and the reemergence, with a changed class of cerebral palsy, of Lasha Murvanadze, the Russia player, who suddenly left the 2004 Athens Paralympics after a protest by Brazil.

As revealed in The Times, there have been serious doubts about many of the competitors, particularly the Russia team, who beat Holland 12-1 on Wednesday with skill levels that the Dutch coach and other nations said were those of professional footballers rather than those with cerebral palsy. “It [their skill] was ridiculous,” representatives from the Brazil and Ukraine teams said.

Paul Cassin, the Ireland manager, said: “Everyone in football knows who I am talking about; there are four to six players from two nations.”

Given such circumstances, it seemed a bizarre decision to ban Malone, who won a bronze medal in the T38 800 metres in Athens four years ago. “He played 30 minutes and had 12 misplaced passes and no shots on goal, he was our worst player so I substituted him,” Cassin said. In fact, Malone, 28, was substituted after 46 minutes on Monday, when Ireland lost 4-2 to Iran.

“Derek’s performance on the field of play appeared better than he demonstrated during the evaluation [on September 4],” the letter from the CPISRA to the Paralympic Council of Ireland read. “He ran symmetrically and jumped symmetrically on the field of play and also squatted down and got back up without any obvious asymmetry.”

Liam Harbison, the secretary-general of the Paralympic Council of Ireland, said that this was “simply not true in any form”, adding that his team had not in any way cheated. “This is very specific to seven-a-side football and to cerebral palsy and I think it questions the ability of the organisation to run elite disability sport,” Harbison said. Malaone, the man at the centre of the storm, said that he was “bitterly disappointed and frustrated” by the developments.

Dickson entered the dispute yesterday, having travelled to Beijing from Hong Kong, and had a crisis meeting with the five nations’ representatives. He said that he would answer their letter this morning, when Russia are due to play Brazil. “It is not something I treat with any degree of lightness,” Dickson said. “Clearly we want people to understand the system and that it is fair to all, which I believe it is.”

The meeting appeared to have smoothed over some of the tension.

“I think it was a start towards a new transparent classification,” Jan-Hein Evers, the Holland manager, said. “We discussed the letter, but it was difficult for him to give an answer because he can’t say my classifiers do everything wrong.”

In theory, this is only an issue for seven-a-side football, which is one of only two Paralympics sports governed by CPISRA. But inevitably it shines a light on the cerebral palsy class at the Games and the general issue of classification. The system of classifying Paralympic athletes according to their abilities and disabilities is similar to how the problem of doping affects the credibility of the Olympics. Most of the sports, and particularly athletics and swimming, have sophisticated, evolving and mutually agreed tests.

They are not without their grey areas, but it is astonishing that CPISRA should have allowed this state of confusion and anger to develop. “This is a football seven-a-side issue, not a cerebral palsy Paralympic issue,” Dickson, who is also member of the governing board of the International Paralympic Committee, said.