British royal Prince Charles is set to sue his former secretary SARAH GOODALL for exposing palace secrets in her forthcoming book THE PALACE DIARIES.

The Prince, who is in the middle of a case with British newspaper The Mail On Sunday over claims it breached copyright by publishing extracts from his private journals, says Goodall's book has broken her confidentiality clause.

Goodall, who worked for Prince Charles during the 1990s, collaborated with author NICHOLAS MONSON, who claims the palace is "overreacting" to the book.

Monson says, "It is going to be a light, breezy book. and they have nothing to be offended about.

"Sarah worships the Prince of Wales, and would never knowingly put her name to something that would upset him."

Palace sources say they will not take the case further until the book is published later this year (06).