Royal & Sunalliance has sold Swinton, its mainly personal lines intermediary, to MMA Insurance for £96m less than the £150m acquisition price it paid 14 years ago.
French-owned insurance group MMA paid £54m to acquire Swinton's chain of 260 high street shops and call centres.
RSA denied it had suffered a £96m loss on Swinton.
Its spokesman Paul Atkinson said: “With the benefit of hindsight we bought Swinton at the top end of market in 1987 before the emergence of direct writers.
“But the acquisition cost has been steadily absorbed by RSA over the years.”
Manchester-based Swinton had a commission and fee income of almost £60m in 1999. The company went through a difficult financial period in the early 1990s, but has achieved increasing profits over the past three years.
MMA chief executive Garry Fearn said the acquisition reflected the insurer's strong belief in expanding its broker-based distribution channel.
“We are firmly committed to distribution by independent brokers and intermediaries, and this purchase does not signify any change to our policy.”
He added: “Swinton is one of the UK's leading high street intermediaries and we are delighted to have been able to acquire such a well known name.”
Swinton managing director Glyn Jones is to leave the business after seven years. His replacement is Patrick Smith, currently chairman of internet intermediary Its4me.