Stuart Neame, the outspoken "Kill the Bill" campaigner and former vice-chairman of Shepherd Neame, has accused the Kent brewer of acting "libellously" following his departure from the company.
Reports in the press last week said that he resigned because of "frustrated ambition" after being told he would not be chairman of the company.
But Mr Neame has fought back, claiming that he left because of a disagreement over the future strategy of the business. He said no-one had ever told him he would not be chairman.
In his letter of resignation he said: "Although the company makes good profits from owning property, our brewing and pub operations are not profitable.
"The uncomfortable truth is that the company would make much more profit if it did not brew beer and run pubs."
He has been calling for a new chairman to change the direction of the company.
"The present structure makes the brewery a sitting duck for an asset-stripper to buy the company for its pubs and close the brewery. This could be prevented by separating the freehold assets from the brewing and pub business."
Speaking exclusively to The Publican Newspaper he said: "The company has written to me aggressively saying I can no longer represent them."
This means that he will no longer be campaigning on issues such as implementation of the Licensing Act and beer duty.
But Jonathan Neame, managing director of the company, has dismissed his claims. He said: "We were as surprised as everyone else by his resignation.
"The entire board is unanimous in remaining vertically integrated. The chairman continues to have the full support of the board."
Chris Maclean, licensee of Shepherd Neame tenanted pub the Plough and Harrow, said: "There is a sense that the brewery has reunited itself since the board meeting. People who were critical of the chairman's regime are now supportive."