Mike Ashley has lost a second senior executive from his Sports Direct retail empire in a matter of days, PA understands.

Company secretary Cameron Olsen resigned on Monday, according to documents filed with Companies House.

His decision to step down on Monday came on the same day Mr Ashley’s retail chief Karen Byers, who had worked for the billionaire tycoon for 28 years, also quit.

Loyal legal expert Mr Olsen had worked for the business for 15 years, including during its listing on the stock market in 2007.

A spokesman for Sports Direct said: “For personal reasons, Cameron has decided to return home to Australia after a great tenure here at Sports Direct.

“Naturally we are saddened he is leaving but he goes with our very best wishes for the future.”

Mike AshleyMike Ashley has now lost two allies in less than a week (Nick Ansell/PA)

He was made company secretary in 2013 at the height of the zero hours contract scandal, when it was first revealed that Sports Direct used the controversial contracts for the vast majority of its staff.

Mr Olsen had previously worked as legal counsel to Sports Direct and was head of legal when he resigned.

The company confirmed he has been replaced by Tom Piper, who has been with Sports Direct since February 2017, according to his LinkedIn profile.

Mr Piper specialises in property law and also becomes head of legal for Mr Ashley’s company.

The company secretary is ultimately responsible for the administration of Sports Direct, especially around regulations and compliance.

READ MORE: Mike Ashley's retail chief quits Sports Direct

During Mr Olsen’s tenure, he was in overall charge of fending off calls from independent shareholders who questioned the company’s poor governance record.

He was also responsible for appointing legal experts to carry out an investigation into workplace practices at Sports Direct’s Shirebrook warehouse, after MPs said staff were working in “Victorian workhouse” conditions.

During the scandal, Mr Ashley admitted to MPs that staff in the warehouse were earning less than the minimum wage due to long queues at security checkpoints.

Mr Olsen’s decision to leave means Sports Direct has lost two senior staffers with a combined 43 years experience working for the company.

On Monday, Karen Byers, whom Mr Ashley has described as “running Sports Direct” left suddenly. He told PA she would be welcome back at any time.

Cameron Oslen's resignationCameron Oslen’s resignation was confirmed with Companies House (Companies House / PA)

The latest senior member of Mr Ashley’s inner team to quit will heap pressure on the company at a time when it is focused heavily on turning stores into the “Selfridge’s of the high street”.

In the last few years, Sports Direct has seen several senior members quit, including chief executive, Dave Forsey; chairman, Keith Hellawell; senior non-executive, Simon Bentley and acting finance chief Matt Pearson.

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Despite the recent exodus, Sports Direct has been making a series of bids for various high street brands, including Game Digital, Debenhams and Goals Soccer Centre.

Mr Ashley has also handed over large amounts of responsibility to his daughter’s partner, Michael Murray, who has been tasked with finding suitable locations for new stores and improving the brand image under the title “head of elevation”.