Britain's national equality body has accused some Premier League clubs of "neglecting" disabled fans after they failed to meet the league's pledge to improve access at their grounds.
Premier League clubs promised two years ago that they would meet basic recommendations - first made in 1998 - by the start of this season.
That 2015 commitment was made after the government threatened to intervene and it is the responsibility of the Equality and Human Rights Commission (EHRC) to monitor compliance.
While many clubs have responded positively, the EHRC has been left frustrated by the lack of progress elsewhere, with Chelsea and Manchester United among those lagging behind. Legal action is possible.
In a statement, EHRC chief executive Rebecca Hilsenrath said the information they have received from some clubs was "of questionable detail and lacked clarity" and this has held up their assessment of "which of our enforcement powers we should use".
Hilsenrath added: "It is clear a significant number of clubs have failed to meet the Premier League's own pledge deadline.
"While some clubs have made progress and taken the bit between their teeth, others have shown a worrying lack of interest in taking this seriously, neglecting the needs of their disabled supporters."
Speaking to the Daily Telegraph, Conservative peer Lord Holmes said those who had believed the 2015 promise "will feel they have been kicked in the teeth".
The nine-time Paralympic swimming champion added that the "miserable result" on access was an "extraordinary stain" on the Premier League's reputation, particularly given its enormous wealth.
According to the newspaper, only 11 of the 20 clubs meet the recommended minimum number of wheelchair spaces at their grounds, with Arsenal, Liverpool, Stoke and West Brom doing the required work over the last year.
The Premier League, however, has reacted strongly to these criticisms, saying they ignore the progress made and the challenges some clubs face, particularly those that do not own their grounds, play at older venues or an in the process of moving.
A spokesman said: "Rapid progress has been made and the clubs' commitment to improve facilities, and other services, is unprecedented in scale, scope and speed by any group of sports grounds or other entertainment venues in the UK.
"A preliminary examination of the data indicates that about 1,000 wheelchair bays have been added across the league in the last two years - an increase of around 50 per cent."
The league, which is publishing its own report soon, also points out that promoted clubs get another two years to meet the commitment - although Brighton already meets the standard - and Newcastle have one more year due to their season in the Championship.
Furthermore, it is understood some clubs dispute the numbers quoted, as the situation is changing quickly.
For example, Manchester United will be trialling their extended platform for disabled fans for the first time when Burton visit Old Trafford in the Carabao Cup on Wednesday.
The work took place this summer but its use is being phased in as it involves moving season-ticket holders.
A spokesman said the club is making "additional assessments" on how to safely integrate disabled and non-disabled supporters in the stands where the works have taken place".
This plan, he added, has been discussed with the EHRC and fans and will continue "behind the scenes" with a goal of full compliance by 2020.
A spokesman for Chelsea said they were still investigating how to lift the low number of wheelchair spaces at Stamford Bridge but were constrained by the ground's "age and design".
He added, however, they would be compliant when they redevelop the ground, which should be completed in 2022.
Mark Atkinson, chief executive at disability charity Scope, told Press Association Sport that a failure to meet basic standards for disabled fans is not just wrong, it is bad business.
"Scope's own research shows that one in three disabled fans who regularly watch their team play at home refuse to go to away matches because of poor facilities," Atkinson said.
"Those clubs are missing out on tapping into disabled people's spending power, estimated at £249billion. The necessary adjustments to meet this pledge are calculated to cost just £7.2million - 0.16 per cent of the Premier League's record turnover of £4.5billion last season.
"Providing basic adjustments won't just vastly improve the experience for disabled fans, it's also a long-term investment which will attract new supporters."