The review follows the departure of the Pizza Hut marketing director, James O'Reilly, who was promoted to vice-president for marketing at KFC USA at the end of last year. Simon Wallace, formerly the marketing manager at Pizza Hut's sister company KFC, replaced him.
Pizza Hut has instructed the media auditor Billetts to draw up a shortlist of agencies to pitch for the account.
PHD is unhappy that Wallace has asked the agency to defend the business so soon after its most recent review; in 2002 it was forced to defend the account from Zenith Media.
Kathleen Saxton, the client development director at PHD, added: "Agencies often talk about standing by our principles with clients and building a partnership based on an equal footing. Sadly, of late this has not been the case with Pizza Hut.
"While it is not a decision any agency ever takes lightly, we feel it is in the interest of everyone at PHD and the agency community at large to make a positive and public stand."
Wallace did not return Campaign's phone calls.
Pizza Hut is a joint venture between Yum! Brands and Whitbread. It has recently embarked on a refurbishment programme to improve its image with customers.
The departure of the Pizza Hut account follows a disappointing recent new-business performance from PHD.
Earlier this month it lost the £33 million planning account for O2 to ZenithOptimedia and it is currently defending its hold on the easyCar business.