The announcement follows the news that the UK firm is cutting around 22 jobs to reduce debt and dispose of non-core assets.
Phillips' will leave on December 5th and will be the company's second boss to leave within a year, following the departure of Mike Heap in March.
An ER representative said that Philips's exit was "amicable," adding: "At this time we need to have a CEO with specific turnaround skills." The firm will announce details of Philips' successor shortly.
Entertainment Rights has been struggling over the past four months. The firm took a £1 million emergency loan in August, and has issued two profit warnings this autumn.
In September, shares fell by 55 per cent after the firm forecast earnings for the year to February 2009 would be down by around £7 million.
A month later, it reported an operating loss of £105 million for the eight months to August 31st, caused mainly by an £83 million writedown in the value of some of its children’s characters and franchises.