Michael O'Kane had been suspended in September after the Irish Daily Star ran images of the Duchess of Cambridge sunbathing sans top while she and Prince William were on vacation in France.
The newspaper issued a written statement saying the uproar among stockholders had led O'Kane to turn in his resignation effective immediately.
The Daily Star is co-owned by Northern and Shell and Independent News and Media. The BBC said the owner of Northern and Shell, media mogul Richard Desmond, had threatened to shut the tabloid down because of the photos.
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