unfair renewal policy

I recently went to renew my Motor insurance policy. I have protected No claims protection. I requested a quote 6 weeks ago and my quote was for £262.00 for a standard no fills policy. I accepted the quote and attempted to pay for the policy. The online app came back with an error please contact call center !! When i got through to an agent, I was told that I had given them all the required information regards my driving claims. He told me I had a claim 2 weeks prior which I had not included. I said that it was a no fault claim so wasn't a claim. He said it had to be included. After me arguing the fact that it was a no fault claim he said he would need to revise my quote.
The new quote came back at £ 780.00. I asked how can a protected policy quote almost treble in price for one claim ? The agent said we don't recognize no claims on renewal quotes. How can an insurance company of Admirals size think this is a fair practice. I won't be using Admiral insurance ever again.