Why does installing Polestar increase my insurance premium?

I have insured my Volvo through M&S Money. It's an XC60 SE Lux D5 AWD which is now one year old and at the annual service I was proposing to have Polestar installed, which is a Volvo accessory that does not affect the warranty and is installed by the Volvo dealership. I telephoned M&S regarding the insurance and was advised that the underwriters would not insure the car at all if Polestar was fitted. Do most insurance companies refuse insurance in these circumstances?

Asked on 30 June 2012 by RS, Gloucs.

Answered by Honest John
It's because it’s classed as a ‘Performance Modification' and many insurers heavily penalise this sort of thing. Lucky you asked first before having it installed. Other readers have had to have Polestar reprogramming removed in order to keep their insurance at an affordable rate.
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