The chaos of the Paralympics that has been marked by race protests and rows concerning the classification of disabilities deepened yesterday after Rebecca Chin, Great Britain's 16-year-old discus thrower, having been reclassified on the eve of the Games, was disqualified and then declassified following her second place in the discus.

Tim Jones, the UK Athletics senior manager for disability, said Chin had been “hung out to dry by the system”. There was better news for David Weir, who received gold yesterday, Britain's first in athletics, for winning the 800 metres on Saturday, after a re-race was abandoned when an Australia protest was withdrawn.

“I was fuming, ready to pack my bags,” Weir, Britain's best wheelchair racer, said. “This is supposed to be a professional Games and it felt like it wasn't done professionally.” Weir said he had hardly slept and avoided Kurt Fearnley, the Australian, who finished second and protested about lane allocation, by having breakfast in his room, until he was told of the reverse at 11am.

Given these problems, it was bizarre that the International Paralympic Committee chose Saturday to announce that a sixth class - intellectual disability - would be returning for the London 2012 Games.

“It is envisaged that the inclusion of athletes with an intellectual disability in future Paralympic Games, beginning with London 2012, will be formally ratified by the IPC General Assembly in November 2009,” an IPC statement read. Intellectual disability, for athletes with an IQ under 75, has been absent from the past two Games, after the Spain basketball team which won in Sydney 2000 was found to contain engineers, university graduates and only two eligible athletes in the squad of 12.

Chin faces a sad trip home to Deganwy, North Wales, and without a classification, an uncertain future. She could be re-presented, but she was good enough at the discus to be selected for the able-bodied Welsh Schools team in July, and that may be her future. She arrived with a lower-leg mobility problem and heard for the first time from classifiers last week that she had mild cerebral palsy and then yesterday that it was too mild to compete at the Games.

She was reclassified from the F44 'les autres' class to the cerebral palsy F38 class over two tests on Wednesday September 3 and then September 5. She competed in the shot put on September 11 and finished tenth.

“That was signed off by the [IPC athletics] chief classifier Richard Brickley,” Jones said. “But then this morning, as she came off the field, I received a phone call from Richard Brickley and he protested [Chin's] classification on the basis of evidence from his viewing classifiers. They had watched her during the warm-up and competition and felt they had seen considerable change, which was not consistent with her classification to an F38 or the way she'd performed in the shot.”

Chin's case again shines a light on the cerebral palsy class. On the day that The Times broke the story of alleged cheating in the seven-a-side cerebral palsy football competition on Thursday, Derek Malone, the Ireland footballer, was reclassified and said to be not disabled enough to compete.

The Times has had assurances from Peter van de Vliet, the IPC Scientific Director, that the situation of athletes being reclassified at a Games should not happen again. “In future we want an athlete to focus solely on their sport and competition and not on their classification,” he said. Asked whether such a system would be in place at the London 2012 Paralympic Games, Van de Vliet said: “Yes. Hopefully before future world championships and Paralympics.” New athletes undoubtedly present the biggest problems for the IPC, but in Chin's case Britain insist that they had her classification approved in June.

“To be classified as a permanent status athlete, you have to be classified internationally, twice,” Jones said. “She was classified first in Manchester at the start of June [at the national trials]. We sought assurances from the classifiers, saying that we don't want to take anyone to Beijing that might be vulnerable to the classification process. We had assurances that no one was likely to cause concern. Eight of our athletes were seen at the process just over a week ago.

“Athletics has some way to move forward in terms of classification. There are a thousand athletes competing here and over 200 of them have been classified here. In swimming there have been only 12 people looked at out of a pool of 500.”

Weir's was the first of four golds for Britain yesterday, which took them past the pre-Games target of 35 to 40. Peter Norfolk defended his singles title in the men's quad tennis. Britain's swimmers with 11 golds, have again enjoyed far more success than the athletics team. Eleanor Simmonds, 13 and already Britain's youngest individual gold medal-winner, added a second by smashing her own world record by seven seconds in 5min 41.34sec to win the 400metres freestyle. David Roberts rounded off the night in style by winning his fourth gold of the Games and eleventh in the Paralympics, in the 50metres freestyle in 27.95sec.