A former policeman said he felt humiliated when new owners took over the firm he worked for and changed his job.
Iain Spence told an employment tribunal it felt like a slap in the face when his responsibilities were taken away.
He claimed he was forced to leave window and door frame company The Abbott Group, which has premises at Heathfield and Golden Cross, near Hailsham, because of the unfair way he was treated.
Mr Spence, who lives at Cowbeech, near Hailsham, is claiming compensation for constructive dismissal.
The company, which has a £20 million turnover and employs about 300 staff, denies being unfair.
Mr Spence told a Brighton tribunal yesterday that his job title was company buyer but he managed transport, personnel and security.
Within days of the firm being taken over in June 2001, he said his duties were gradually removed. When told he was no longer responsible for security, he left.
He said: "I am a retired police officer and I felt this was a slap in the face and the last straw. I felt humiliated. I felt I had been badly treated by the new owner. I was being reduced to no more than an invoicing clerk."
The company described Mr Spence as an administrator and said he had no management authority.
David Hatter, the firm's financial director, said: "He never formally held a management position so it could not have been taken away from him. There was no intention of reducing his status in the company.
"We saw him as a valuable member of staff with an important, ongoing role. We were very surprised by his resignation. There had been no warning he was unhappy."
The hearing continues.
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