Smithfield CEO John Antcliffe is leading Davies' riposte to the claims, which The Sunday Telegraph attributed to the 'M&S camp'.
M&S's retained agency is Tulchan Communications.
Davies' departure was announced just two hours after the retailer unveiled its best trading results in two years, and overshadowed interpretations that the retailer might have turned the corner.
Davies, who earned a base salary of around £1m a year at M&S, has denied reports that he demanded £150m to stay.
M&S has bought Per Una from Davies for £125m. But as the fashion brand operated as a standalone business with separate offices and staff, other key employees may also leave.
Melanie Davies, his daughter and business associate, and Per Una head of merchandising Andrea White resigned on the same day as George Davies.
'It is not true that I resigned because of differences over money,' he told PRWeek. 'I resigned because having sold Per Una to M&S I committed to work at Per Una for a period. I do not enjoy working within a large corporate group so, once my commitment is honoured, I will leave.'
Davies is also a former chairman and chief executive of Next. He was brought into M&S by ex-CEO Roger Holmes and chairman Luc Vandevelde to revitalise its clothing offering.
Per Una has annual sales of around £350m, accounting for almost a quarter of womenswear sales at M&S, and is one of the retailer's best-performing divisions.
Second-quarter sales at M&S were much better than expected, with like-for-like sales up by 1.3 per cent for the 12 weeks to 1 October.