Sports Direct’s billionaire founder, Mike Ashley, is standing by his under-fire chairman, Keith Hellawell, despite independent shareholders in the sports retailer voting to oust the former police chief. .

An unprecedented 57% of independent shareholders failed to support Hellawell at the annual shareholder meeting on Wednesday, but Ashley insisted his chairman was staying put, for at least another year, and they would work together to improve the way the sports chain is managed. .

At the sometimes bad-tempered meeting, Ashley at one point said the retailer’s problems had been caused by the Unite union and hinted that he might himself walk away from the company he founded in 1982 if he was unable to improve the way the firm is run.

There was also a major protest vote against Sports Direct’s three other non-executive directors. More than 30% of independent shareholders failed to back their reappointment amid widespread concern that they had failed to hold Ashley to account.

At the packed meeting of more than 120 people at Sports Direct’s head office, alongside its controversial warehouse in Shirebrook, Derbyshire, Ashley was challenged by investors and unions over the treatment of workers. The company has been under intense scrutiny since a Guardian investigation last year, which revealed that Sports Direct was failing to pay the national minimum wage to warehouse workers.

Under new financial regulatory rules, the company will have to hold a second vote in 90 to 120 days’ time at which Hellawell’s reappointment can be pushed through with the backing of Ashley’s 55% majority stake.

Hellawell insisted he was justified in carrying on in the £155,000-a-year role. “Investors recognise my integrity,” he said. “My position is not untenable. The majority of shareholders in this company support me”. However, he said he would step down next year if independent investors still wanted him to go.

“I am here to prove to the majority of independent shareholders who don’t support me that I am making a valuable contribution to this company and over the next 12 months I’ll be judged on that contribution,” he said.

Ashley said Hellawell’s years of experience in working with him would help implement a turnaround plan announced earlier this week after months of pressure from shareholders, unions and the media.

“Keith knows my strengths, and my weaknesses, and we’re beginning to learn some of the company’s weaknesses, together,” he said.

With his voice almost breaking, he pleaded with shareholders to give him more time: “So, we’re going to fix it. Please give us 12 months to fix it. What difference is 12 months?”

Ashley admitted that he had made “totally unacceptable” mistakes in the running of the warehouse and admitted he might quit the business himself if he could not deliver improvements: “In the end, if I keep failing and keep failing and keep failing, it’ll be best for everybody if I go. But give me some time to see if I can fix the problems first, please.”.

Shares in Sports Direct fell more than 10% to 314.4p on Wednesday as investors expressed disbelief that the company was resisting change at the top despite promises to listen to shareholders.

The company warned that profits would be just £300m, 21% lower than expected this year, as costs rise and it spends more on buying property.

Sacha Sadan, the director of corporate governance at Legal & General Investment Management, called on Hellawell to step down immediately to be replaced by an external independent chair.

“Following Sports Direct’s recent report on its own shortcomings, as well as the large independent shareholder vote against the chairman’s re-election, it is clear the board needs to enact significant change in order to earn back shareholder trust,” Sadan said.

On Tuesday, Sports Direct tried to respond to criticisms by revealing plans to offer shop workers the option of guaranteed hours contracts instead of zero hours. It said it would suspend the notorious “six strikes and you’re out” policy in its warehouse which meant workers could lose their jobs for relatively minor infringements.

At the meeting in Shirebrook, Steve Turner, the assistant general secretary of Unite, said he would not be surprised if only a few workers took up the offer of 12 guaranteed hours a week as most were working much longer shifts.

His criticism prompted an angry outburst from Ashley, who blamed the Unite union for the company’s problems.

Ashley said: “This is probably your fault we are in this situation because we can’t talk to you in an open manner.

“I’ve made a commitment to make a difference and I’m trying so don’t pull me down. Don’t do the whole showboating thing. It will make me turn away and the only people who suffer are people that work at Sports Direct.”

Nearly 21% of all shareholders voted to support a union-backed resolution calling for an independent review of working practices at Sports Direct – a highly unusual level of support for shareholder resolution. The report published earlier this week was compiled by Ashley’s lawyers.

Janet Williamson, the chair of the Trade Union Shareowners group said: “Today’s shareholder uprising should act as a cautionary tale to other employers. Sports Direct’s reputation has been dragged through the mud and its share price has taken a hammering.

“The company must now commit to holding a genuinely independent investigation into how the company treats its workers. Without wholesale changes to working conditions, Sports Direct risks finding itself back in the dock.”

Speaking after the meeting, Hellawell told the Guardian that Sports Direct’s board had not moved to make changes before the Guardian investigation, despite years of criticisms, because they had not been given correct information about working conditions.

“We were acting on the information we had,” he said. “One of the biggest disappointments is we found that information was not correct.”