Wishing to have more privacy at her £3.5m Surrey mansion with husband, Ashley the X Factor judge applied for planning permission to build an underground swimming pool complete with gym, spa and plant room in 2008.
As well as preventing outsiders from intruding on the couple's intimacy the extension was to be a work out space where the couple could maintain their health and fitness.
A government inspector has now ruled however that that the addition is not "essential".
The planning officer went on to say that it would be a "disproportionate addition to the house."
The couple have previously made successful applications for a three-storey extension, a-five-aside football pitch, garden pavilion, two oak-framed garages and new timber gates with lamps.
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