Lindsay previously owned 86 per cent of the business, which is perhaps most famous for football-based social media work with the supermarket Iceland but has also worked with Comic Relief, Reebok and Garmin. The remainder of the business was owned by co-founder Sarah Halton.
Under the new arrangement, 26 per cent will remain in Lindsay's hands, while two stakes of five per cent each will pass to MDs Sam Gregory and Mary Harding. The rest will be owned by the firm's 60-strong workforce (including Halton) through The Tangerine Partnership. The Trust will be chaired by Halton.
Every year, a proportion of the firm's profits will be paid to all employees who have passed probation, being on a formula taking into account salary and years of service.
Last year, Tangerine's operating profit was £438,054 - around a tenth of which was paid to staff through an existing profit share scheme, while dividends totalling £314,355 were paid to directors.
Lindsay told PRWeek she had long promised to make such a switch, saying: "Our values – 'do great work; treat people properly' - have always been central to everything we do and we wanted to find a way to ensure we can continue these into the future for the benefit of all.
"We'd been spending quite a long time thinking about what we wanted to do, and it was actually our accountants who came up with this and we just thought 'wow' - it just seemed absolutely perfect," said Lindsay.
Lindsay did not disclose details of the deal under which the majority of her stake was transferred, but said she was not seeking an exit from the business, saying: "It's about whats next for the business, it's absolutely not about anyone going anywhere."
The firm celebrates its 15th birthday today.
Deb Oxley, CEO of the Employee Ownership Association, said of Tangerine's move: "Some of the UK’s best companies are looking to employee ownership as a great business model to adopt which helps them to attract and retain the right talent, which in turn helps to develop and maintain great relationships with clients as well as protecting the brand, ethos and contribution the businesses makes to its local economy for future generations."
In 2015, Lindsay was named an MBE for her services to business, in particular creating The Juice Academy, a social media apprenticeship programme that has created more than 200 jobs for young people to date.
In 2013, Forster Communications opened up ownership to staff. Other agencies with employee ownership plans include Lewis, whose website claims it has "the largest employee ownership scheme in the industry, with over 70 partners and counting", and Lansons Communications, where ownership is split among a third of its 110-plus staff.