Knight Banner owns Precise, EDS, EPCA, ClipAbility and Media Report, which each specialise in monitoring certain sectors. It represents about a quarter of the media monitoring market in the UK with annual sales of £16m.
The deal, led by media entrepreneur Peter Harkness and backed by 3i and the Royal Bank of Scotland, sees founders Martin Knight and Chris Banner relinquish all equity in the firm.
Incoming chairman Harkness said the deal would see long-term investment in Knight Banner, with its directors holding more than 45 per cent equity in the group and funding secure for at least seven years.
Harkness, who previously worked with 3i on deals at WHY Publications and Butler Group, said the Knight Banner brands would remain separate.
Keir Fawkus, managing director of Precise, the largest of the group's brands, said the immediate impact of the deal would be minimal. He added that it would accelerate the addition of media sources to its services and introduce new products.
'We have just under 5,000 sources and would like to get that up to 7,500 within two years,' said Fawkus. He added that growth would come predominantly from UK media, including online sources.
Fawkus said it was too early to say which products were in the pipeline but the firm would look at expanding media evaluation and press release distribution services.
Harkness and Fawkus are joined by incoming business development director Jon Shepherd, who moves from rival firm Durrants.