Dore has been named head of corporate PR and is on a 13 month contract, covering for Clair Foster who is on maternity leave.
Reporting into Flic Howard-Allen, M&S's director of communications and CSR, Dore will be responsible for the management of all financial and corporate media and the retail giant's seven-strong corporate PR team.
Dore said: ‘M&S is one of the most iconic brands in the country and in the press all day, every day on a huge variety of issues. The corporate PR team will continue to manage the brand's reputation on everything from green issues to City matters.'
Dore and fellow MD and co-founder Debbie Wosskow sold Mantra PR to Loewy Group in mid-2007. Wosskow left the firm in February this year, with Dore departing during the summer.