"We had a difference of opinion about the advice provided," he said.
Southern Cross, the country's largest health insurer, had been using Praxis Public Relations for its general work before the storm broke.
Praxis is understood to be one of the groups advising the board.
It is unclear who will succeed Shandwick in the prime troubleshooting role. Several firms are believed to be pitching for the account, worth well into six figures.
Many believe Raynish & Partners is being lined up for the work. Jenni Raynish, who is advising Southern Cross chairman Hylton LeGrice, could not be reached for comment last night.
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