Troubled sportswear retailer Sports Direct has lost its only senior non-executive director after a row over the company's alleged failure to clean up its act on corporate governance.

Chris Bulmer, who joined the owner of Lillywhites and Sports World ahead of its February flotation, had clashed repeatedly with billionaire founder Mike Ashley and other directors.

She resigned yesterday after a boardroom bust-up over corporate governance standards. She was particularly frustrated at the company's failure to appoint a new chairman to replace David Richardson, who quit in May citing boardroom disagreements.

Ms Bulmer, who previously worked with Mr Richardson at leisure group Whitbread, had stood out against a proposal that Simon Bentley should move from his current role as acting chairman to become chief executive of the company.

Last night it transpired that candidates for the chairmanship role had been told that on the appointment of a chairman, Mr Bentley would become chief executive. Not surprisingly, no candidate was prepared to accept the job on that basis.

Ms Bulmer, also a non-executive at drinks group Britvic, had expressed concerns on several occasions leading up to this week's clash, but as Sports Direct's only remaining independent non-executive director she felt obliged to stay to ensure the appointment of a new chairman.

Things came to a head at a board meeting on Wednesday over the board's decision to appoint two new non-executives. Deciding it was impossible to perform her own non-executive role, Ms Bulmer told the board of her intention to leave.

"Independent directors need to insist on the corporate governance rules being applied correctly. Otherwise what's the point?" she said last night.

Her frustration echoes the City's criticisms of Sports Direct, whose shares have halved since it became a publicly listed company. It has been attacked for failing to meet proper standards of transparency in its financial reporting as well as over what one analyst recently described as a "scatter-gun" approach to acquisitions.

Shares in the company closed 2p higher at 147p yesterday, in part reflecting the fact that news of Ms Bulmer's departure was accompanied by the announcement of two new non-executives. Sports Direct said property entrepreneur Malcolm Dalgleish and former Reebok employee Dave Singleton would join immediately.

Sports Direct has fallen from grace spectacularly since it floated, earning sports tycoon Mr Ashley £929m. It has issued two profit warnings and a dearth of information has worried and angered the investor community. An unabashed Mr Ashley, owner of Newcastle United, inflamed matters by dismissing frustrated shareholders as "cry-babies". He has also clashed repeatedly with directors and advisers.

Sports Direct did not return calls.