Scott Kilday, 35, said he was left "horrified" on finding a listening device hidden within artificial flowers.
It came shortly after he was asked to resign from his post as a director at Miss Mone's MJM International company based in East Kilbride, South Lanarkshire.
Mr Kilday was later allegedly told the bug had been planted for "business strategic reasons".
Mr Kilday made the accusations on the first day of his employment tribunal in which he is claiming unfair dismissal against MJM.
The hearing in Glasgow was told how matters became "difficult" within the lingerie company after Miss Mone split with her husband and business partner Michael in December 2011.
Mr Kilday said: "It all became a bit disjointed and basically there came a time Michelle and Michael could not sit in the room together.
"With both being majority shareholders it was very difficult to get any decision made, which ultimately was the fall of the business."
Mr Mone eventually left MJM days before another company - MAS Holdings - bought into the business in February this year.
Mr Kilday, of Glasgow, said that around the same time Miss Mone asked him to resign as a director.
He told the tribunal: "She said that MAS had asked for me to resign as director for the sale of the company to go through.
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