Staff will have to reapply for their jobs in the wake of PremierLine's management buyout (MBO).
It is understood that staff in areas of the business where their job was "at risk" would have to re-apply for their jobs.
Also 20 staff are being made redundant, affecting every department.
PremierLine's insurance will now be underwritten by Allianz Cornhill, which, according to a source close to the deal, had offered to underwrite the current policies subject to a 12-month review and a cost-cutting of £1.5m.
The source said this led to the decision to cut staff. Before the MBO, Zenith underwrote PremierLine's insurance.
PremierLine was unavailable for comment.
PremierLine managing director Barrie Wells bought the company from holding company Acott, Tilley & Wells Holdings, which owns the Zenith insurance group. It was launched early in 2002 with 6,400 customers.
In a statement last month, the commercial insurance specialist said it would continue to focus its business in the SME market.
"We now plan to extend our product offering. We will be in a strong position to underwrite larger businesses, go into new market sectors and offer additional complementary products and services," said Wells in the statement.