Thomas will oversee the strategic direction of the agency, working with existing clients such as Gocompare.com and Barclaycard, as well as develop new business.
When she starts on 1 May, Thomas will report to Paul Hammersley, the UK group chief executive of Dare’s parent, EDC Communications.
Before being promoted to managing director of Saatchi & Saatchi in January 2012, Thomas was the head of account management at the agency from 2010.
Thomas’ career includes a stint as the client services director at Abbott Mead Vickers BBDO from 2007 to 2010, and as an account handler and then head of account management at Lowe Lintas for three years until 2007.
After seven years as a soloist at the South African Ballet Theatre, Thomas started her advertising career in her native South Africa in account management at TBWA\Hunt\Lascaris and The Jupiter Drawing Room.
Hammersley said: "Leigh has a fantastic pedigree of agencies. The key for us is that she has experience managing big clients and big groups of people. I’m confident that she can build big client relationships and she will help the agency move forward."
Thomas said: "I am utterly fired up at the prospect of joining Dare. It is a uniquely progressive brand and agency model but, more importantly, is filled with courageous, intelligent people, with credibility in traditional, social and technology skills. That space is the right place to be for this generation of consumer and client."