Sports Direct has lost its battle against former MP Iain Wright after parliamentary authorities refused to investigate claims that he helped wipe millions off the retailer's share price and triggered violent assaults on shop staff.
The explosive allegations were made as part of a formal complaint to Parliament about Mr Wright's conduct when he led an inquiry into Sports Direct's working practices.
In a letter to Kathryn Stone, the Parliamentary Commissioner for Standards, Sports Direct's chairman Keith Hellawell claimed the former Labour MP presided over a "media circus" while chairman of a powerful select committee.
However, the Press Association has learned Ms Stone immediately wrote back to the company saying she would not investigate the case.
It is not within Ms Stone's remit to investigate former MPs, or complaints relating to the conduct of parliamentary proceedings.
A spokesman for Sports Direct said: "We have to respect the decision of the Parliamentary Commissioner for Standards, however the fact remains that Iain Wright misled and lied to Sports Direct."
Mr Wright's investigation of working conditions in Sports Direct - which saw its billionaire owner Mike Ashley hauled in front of MPs - concluded that its Shirebrook warehouse was run like a "Victorian workhouse".
However, Sports Direct said Mr Wright lied to the company about the timing of a visit to its warehouse, and failed to act objectively because he did not disclose a donation from the Unite union, an active party in the inquiry.
Sports Direct also claimed the inquiry triggered attacks on staff.
"On one occasion, the calls included a threat to rape a member of staff, and another caller said that they hoped Sports Direct employees would be diagnosed with cancer," Mr Hellawell wrote.
"Our staff were also subject to a number of physical assaults and verbal abuse in our stores.
"This coincided with a catastrophic fall in the share price of Sports Direct, which depleted tens of millions of pounds from the value of our share bonus pool for eligible staff."
Mr Wright stepped down as an MP before last year's election, and is now working at the Institute of Chartered Accountants in England and Wales.