The three firms are Premier Network, Mansfield Begbie and Premier Mortgage Services.
The network now has 196 firms under its umbrella, comprised of 394 individual advisers.
Richard Adams, managing director of Stonebridge Group, said: “We are very pleased to be welcoming these three new businesses into the Stonebridge Group fold and are delighted they have seen the benefits and opportunities to be secured by joining us.
“All three firms are ex-L&G firms and our strong relationship, and our preferred partner status, certainly helped highlight what we can offer to these existing ARs.
“Our recruitment levels have been strong throughout the year and we still have a significant pipeline of firms and individuals who are currently being approved prior to joining us.
“2015 has certainly been a landmark year for Stonebridge and we have many plans and propositions to launch over the next 12 months.”
The Premier Network is based in Enniskillen, Northern Ireland, Premier Mortgage Services is Nottingham-based and Mansfield Begbie is based in both Luton and Swindon.
Stonebridge also has a further 30 advisers currently in the process of being approved before officially joining the network.
Michael Ilston, director of Premier Mortgage Services in Nottingham, said: “We spent a long time looking at a variety of options having been associated with L&G for such a long time.
“We feel that joining Stonebridge is a good match for our mortgage and protection business and should help us to build on what has been a very good year for us.”
In June Shepherd Direct, the national property services group with interests in surveying, valuations, lettings and estate agency, acquired a minority stake in Stonebridge.
