Mr Warnock, who retired from Aberforth in 2008 after nearly two decades with the Edinburgh fund management house, highlighted Seneca Investment Managers' "big plans" as he was unveiled as chairman yesterday.
The recently-formed Seneca Investment Managers, part of Seneca Partners, last month announced the purchase of the Miton Capital Partners business from Miton Group for up to £6.4 million, a deal which brings with it about £450m of funds under management.
The Liverpool-based Miton Capital Partners business manages funds including Midas Income & Growth Trust, the CF Miton Distribution Fund and the CF Miton Diversified Growth Fund.
Seneca Partners was formed in 2010 by Ian Currie, Stuart Eaton and Alex Dymock to provide investment services to wealthy individuals and families in the UK, including entrepreneurs.
Mr Warnock, who has a portfolio of non-executive roles including directorships of Greenock-based packaging company British Polythene Industries and Standard Life European Private Equity Trust, said: "I am both privileged and excited to have been offered the role of chairman. Stuart has big plans for Seneca Investment Managers, and my role will be to help those plans come to fruition in the years ahead."
Mr Eaton, who previously held senior roles at Newton and Insight Investment Management and is chief executive of Seneca Investment Managers, said: "David is one of the most recognised people in the industry and it is a real coup to have him on board. Our goal is to turn Seneca Investment Managers into a leading brand within UK financial services and his experience, expertise and contacts will certainly make that a lot easier to achieve."
Mr Warnock, who worked with private equity company 3i and Edinburgh investment house Ivory & Sime before co-founding Aberforth, is also chairman of Troy Income & Growth Trust.