It is not known whether Meakin will be replaced.
Meakin said: 'I am very sad about leaving, but I had to resign. A series of things combined and made me realise it would be difficult to carry on.'
His resignation comes just months after board director Charlotte Clarke left Cairns & Associates to go freelance, after six years with the firm.
The agency's clients include Vaseline, Sure, Impulse, Timotei and Foster's. It was also recently hired to promote a Phil Tufnell DVD for distributor Warner Vision in the run-up to Christmas.
New York-based Cairns said she would be increasingly involved with the UK office in coming months.
But she also signalled a shake-up at the agency. 'We will be playing to our strengths in two distinct areas – the lads' market, with accounts such as Foster's, and products for women,' Cairns said.
Meakin is on gardening leave until the end of the year. He told PRWeek he was considering his options, but expected to take another consultancy role.
He joined Cairns & Associates in February from The Communication Group, where he was consumer MD for five years. He quit TCG just two weeks after he was promoted to the company's board (PRWeek, 19 November 2004).
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