The UK P&I Club will replace insurance giant AIG in underwriting the growing fixed-premium protection and indemnity business of Thomas Miller Specialty.
Thomas Miller, manager of the UK P&I Club and seven other mutual businesses, said it would end its three-year agreement with AIG in January next year.
It has been growing its fixed-premium offering through offshoot Thomas Miller Specialty's acquisition of established players Hanseatic, Osprey and Lodestar.
"We have strong links with the UK P&I Club and it is the ideal partner to underwrite our fixed-premium book," said Thomas Miller Specialty chief executive Danielle Champion.
UK P&I is one of the most financially robust P&I mutuals, with around $500m in free reserves and a AAA-rated capital adequacy.
Through the move, it will join the West of England, the American Club and North of England P&I in targeting the fixed-premium business to diversify income streams.
UK Club chief executive Andrew Taylor said: "The working partnership between us will further cement Thomas Miller as one of the leading providers of P&I insurance and provide a comprehensive product offering to our mutual client base."
Fixed-premium P&I insurance focuses mainly on small and specialised vessels. It is priced purely on commercial terms and involves an assessment of the risk and claims record of insured parties.
Fixed-premium pricing is not affected by the considerations of mutuality that occur in the mainstream P&I market.
