Scott Kilday, 35, who left the board of MJM International after its takeover by MAS Holdings in February, was not acting in the best interests of the firm, the Glasgow tribunal where he is claiming unfair dismissal was told yesterday.
MJM chairman Eliaz Poleg said he wanted to "control" him before he left the company and it was not in the company's interest for him to leave the day after the takeover deal in February this year.
Mr Poleg, 62, said Mr Kilday was demanding compensation and denied that he was planning to work for Miss Mone's former husband, Michael, who left East Kilbride-based MJM before the sale.
However, Mr Kilday, who found the bug hidden in artificial flowers, did in fact go to work for Mr Mone's lingerie firm Pendulum Apparel, Mr Poleg said.
Confirming the device was arranged by Miss Mone and fellow director Kanishke Manakkara, Mr Poleg told the hearing: "This was not about me or about Mrs Mone or about anybody, this was only about the company needs."
Under cross examination by Mr Kilday's representative John McMillan, Mr Poleg said he was concerned that Mr Kilday was doing things that were not supportive of MJM.
When asked specifically what his main concern was, Mr Poleg replied: "That he will share confidential information with competition."
Mr Poleg earlier admitted that he was under stress in the days following the deal and was worried that it would not 'fit together.'
He added: "He (Kilday) knows he's the only one who can operate the company in the short term because the new investor is an overseas company."
He described Mr Kilday as "vital" to the company and said the thought of what to do about the situation was "breaking my mind."
Mr Poleg added: "I was begging him to stay for a few months to see if it works." He admitted that he thought Mr Kilday was working to a different agenda to his.
Mr Poleg said: "Everything he did was serving somebody else but, for sure, not MJM."
The witness said Mr Kilday had worked with the Mone family for 10 years and that he was closer to Mr Mone.
Mr Poleg added: "I said I need to get some time and try and find a solution but I have to control what this guy is doing."
He phoned Tony Caplan, Miss Mone's lawyer, and told him what he had in mind. Mr Poleg said he was told that it was "not common" but was "not illegal".
The tribunal heard he then thought about it and discussed the bug plan with Miss Mone and Kanishke Manakkara.
However, Mr Caplan, a director following the takeover told the hearing: "Eliaz was very concerned and I thought for justifiable reasons."
He added mischief could be caused by people who were on Michael's side, including Mr Kilday.
The tribunal heard Mr Caplan spoke with Mr Poleg on the phone about his concerns and planting the bug in Mr Kilday's office.
He said: "With reservation I indicated they could probably run with this. I actually wasn't involved in the final decision."
It was suggested to Mr Caplan that he had two conversations with Mr Kilday in his office, including one where he returned to "gather ammunition" because he knew the bug was there. Mr Caplan denied this. A judgment will be issued at a later date.