Absolute Rip-off

I just received two letters from Dialdirect Insurance informing me that my premiums will be increasing by 21.9%. I find this absolutely ridiculous and refuse to accept it, as I have not had a claim in 2 years, my risks have not changed and I do not know how they justify it. Apparently they have increased the cover by 10% - why do they increase the premiums by 21.9%? Surely this is *******? The current CPI is 6.5%. I refuse to pay any increase above CPI. My salary is definitely not increasing by 21.9%. I am most certainly going to shop around and also bring this to the attention of Carte Blanche as this is unacceptable.