The pressure on Mike Ashley to address concerns over working practices at Sports Direct has been ramped up a notch after another shareholder group called for an independent review of how the business is run.
The Investor Forum, consisting of influential investors holding assets worth more than £14 trillion, has urged the retailer to "undertake a wide-reaching independent review of the entire governance practices at the company".
The unprecedented criticism by the Forum comes amid growing shareholder unrest over the power wielded by MrAshley, who owns 55% of the group and is deputy executive chairman.
And the intervention comes after it was revealed that Sports Direct's accounts fail to disclose that international deliveries are run by Mr Ashley's brother, John.
Forum director Andy Griffiths said: "It is highly unusual for the Investor Forum to consider it necessary to make public their concerns and recommendations in this way.
"In prior situations we have always managed to work privately with companies to create effective long-term solutions.
"We do not take this step lightly and, whilst we welcome Sport Direct's move to hold an open day, we still have not received an appropriate level of commitment to respond to investor concerns and, as a result, the usual options have been exhausted."
He added that the business requires "fundamental reform".
Sports Direct is also facing calls from a growing list of investors asking for an independent review into working practices following Mr Ashley's grilling by MPs in June.
Mr Ashley, who is also the owner of Newcastle United football club, told MPs from the Business Select Committee that staff were not paid during security searches at the end of their shift, meaning they took home less than the minimum amount required by law.
The Forum added: "Following Mike Ashley's appearance at the BIS Select Committee, shareholders requested that the board commit to an independent and comprehensive review.
"The Forum was clear that the review would have to be independent, comprehensive and, as recommended by the BIS Committee report, cover all aspects of corporate governance across the business, not only employment practices.
"Governance failings are clearly resulting in declines in operating performance and long- term shareholder value and, given the lack of progress and the broader impact on all stakeholders, the Forum now considers it important to make public its recommendations to the Sports Direct board."
For its part, Sports Direct has said the findings of a separate review carried out by RPC would be published in the week beginning September 5, and it would conduct a review of its board of directors by next April.
Yesterday, Sports Direct announced that it will hold an open day for the public on the day of its AGM on September 7, when it is expected to face a barrage of criticism from unions and shareholders.