Intrinsic Financial Services has taken a minority stake in Charles Derby.
Charles Derby is already an appointed representative of Intrinsic but the stake will offer “stability and security”.
With more than 70,000 clients, Charles Derby has more than £1.3bn in assets under advice and 350 advisers across the UK.
Charles Derby chairman and chief executive, Chris Fautley, said: “In Intrinsic, we have secured the continued backing of a business with the necessary scale to support a national financial planning firm of our size.
“Today’s announcement guarantees some level of continuity and stability and will help Charles Derby continue to deliver for all our clients, staff and advisers.”
The deal will not materially impact the day-to-day working relationship between Charles Derby and Intrinsic, and the business will continue to operate as an appointed representative of the network.
Andy Thompson, chief executive of Intrinsic, said: “The network’s practice buyout scheme will continue to support businesses within the network to pursue their own acquisitive growth strategy.
“Today’s announcement represents an extension of that commitment to invest in the future of the industry, offering the network’s largest firm, Charles Derby, the opportunity to realise an investment in their business which will allow them to continue their growth journey.”