Greater Manchester Police has been asked by the Metropolitan Police to review its "Plebgate" investigation.
The Met said the move is standard practice in a high profile investigation.
More top news
Wintry weather into the weekend
Jeremy Hunt could impose controversial new contracts for junior doctors by Monday, ITV News Political Editor Robert Peston has learned.
A new video has emerged online purporting to show a four-year-old British boy blowing up a car and killing three prisoners on behalf of IS.