ITV News video report by Business Editor Joel Hills
Mike Ashley confirmed Sports Direct had failed to pay some staff the minimum wage and said things had happened at the company that "shouldn't happen" and were "unacceptable".
The billionaire tycoon told MPs the claims of mistreatment and poor working conditions that led to his delayed appearance in front of the Business Select Committee showed Sports Direct has "definitely outgrown me".
"Some things have come as a bit of an unpleasant surprise," he said after an early review into work practices, which he claimed would never end.
The Newcastle United owner also clarified he wasn't "Father Christmas" but could do a "better job" for workers than the unions.
"I’m not Father Christmas - I’m not saying I’ll make the world wonderful.”
He also confirmed HM Revenue and Customs is investigating the sports chain over its failure to pay a national minimum wage.
He faced serious questions over working practices at its flagship Shirebrook warehouse in Derbyshire, including its six-strike issue policy, the use of zero-hours contracts and severe fines for lateness.
In a 90-minutes-plus-extra-time appearance in front of MPs, the tycoon also said:
Sports Direct broke the law by paying staff less than the minimum wage because of bottlenecking at security which delayed staff clocking in and out
The chain's six-strike policy on worker dismissals is fair "if it is executed correctly"
A fine of 15-minutes' pay for every minute employees were late on shift is "not fair"
Sports Direct staff had been "over-quick to pick up the phone" after it was revealed that 110 ambulances were called to its main warehouse in the last three years
A review into working practices at Sports Direct was underway but will never end
He wanted to see more of his staff on full-time contracts as he confirmed that four in five workers were on zero-hour contracts.
He could "see value" in making exployee surveys compulsory but said he could do "a better job than Unite" in issues with workers.
He would implement a number of changes to working practices within 90 days and promised to write to MPs if the time frame needs to be extended
He attempted to buy BHS before the firm was confirmed as heading into liquidation.
Mr Ashley confirmed the buck stopped with him as the company boss but also played down his responsibility for individual claims of malpractice cited by the panel of MPs.
"I cannot be responsible for every little thing that happens at Sports Direct," he said, while adding: "I can only do my best and my best may not be good enough."
Prior to his appearance Mr Ashley admitted in a letter to the firm's 27,000 workers that there had been issues with security and search processes at the Shirebrook warehouse.
He told staff he wanted to "defend the good name of Sports Direct and all of yourselves. Because I have always believed that we have nothing to hide".
Mr Ashley announced in December he would personally oversee a review of working practices at the Shirebrook warehouse in response to serious allegations from a Guardian investigation.
Ashley 'jolly' in giving evidence to MPs
ITV News Business Editor Joel Hills noted the exchange between Mr Ashley and MPs - billed as a showdown - proved more affectionate as the tycoon played down claims of sinister events.
But Mr Ashley's evidence was watched carefully by those with vested interests in the company, some of whom were far from impressed.
Unions claims Sports Direct relies on 'exploitation'
The Unite union earlier criticised Sports Direct, claiming its business model had "exploitation" at its heart and its "six-strikes and you're out policy" had established a "culture of fear".
The list, tweeted by Joel Hills, includes issues like "excessive talking" and taking too long in the toilet.
The union's Steve Turner told MPs the retail chain's bosses displayed "arrogance and contempt" for their staff.
But the recruitment agencies which provide workers to Sports Direct said conditions were a "normal working environment".
The agency representatives told MPs that Sports Direct's six-strikes policy was there to "help" workers and said they were unaware of mistreatment of workers.