Trevor Wheatley, a former executive with an Emerson subsidiary called Control Techniques, was last month told by the High Court that he could not work for or own shares in Focus Dynamics, another engineering firm.
Emerson had argued that Mr Wheatley's involvement with Focus violated a non-compete clause in his contract.
However, Mr Wheatley is planning to appeal against the ruling, which bars him from working for Focus until 20 December.
Meanwhile, he is also pursuing a claim for unfair dismissal against Emerson after he was sacked by the company in May - just one-and-a-half years into a five-year, $20m (pounds 12.3m) contract.
"Emerson spent an inordinate amount of time and money to stop me competing with them for another 20 weeks," Mr Wheatley said yesterday.
"I can only conclude they were doing that as a smokescreen for the wrongful dismissal case.
"They have used their deep pockets to finance their bully-boy tactics. It only makes you wonder how far these people will go."
News of the battle is set to further embarrass Emerson, which has already had its reputation in the City tarnished by its attempt to take control of Astec (BSR), the electronic components group in which it holds a 51 per cent stake.
Earlier this year, a consortium of institutional shareholders in Astec took Emerson to court for unfairly prejudicing the rights of its minority shareholders. However, the court threw out the case.
Mr Wheatley said that the whole episode had made him all the more determined.
"After the shabby way Emerson have treated me they have spawned the most determined competitor they have ever had," Mr Wheatley said.