Property management and insurance group Hercules Property Services has bought housing association property broker DOR (Northern) for about £4m.
Hercules's acquisitions over the past 18 months now total £40m as it strives to dominate niche markets.
Macclesfield-based DOR, owned by David and Olga Owen, turned over £1.1m last year. David Owen will remain on the board of DOR.
Hercules now owns 45% of the housing association insurance market, with its housing association subsidiary FARR.
Hercules managing director Rob Plumb said: "Hercules acquired FARR in 2000 with the aim of expanding into other areas of the property insurance market.
"The acquisition of DOR will serve to strengthen Hercules's strategy and position in the UK housing association insurance market."