As if car insurance wasn't bad enough already, the excesses for drivers with three points appear to be shooting up – and six points could see insurance refused.

According to research carried out by RoadPilot, insurance premiums for offenders are significantly higher now than just six months ago. The cost of the average insurance premium for a speeder with three points is now £90 higher than for a driver without a conviction, up 17 per cent from the £77 average penalty in December 2011.

The findings also point to insurance premiums rising faster for female speeders than for their male counterparts. The company's research of 10 leading insurers found that if a female driver incurs a three-point speeding conviction her premium would increase, on average, by 15.7 per cent (or £90) compared to a quote for the same person without a speeding endorsement. This is significantly more than the increase for a female speeder six months ago (up by 13.4 per cent, or £69).

Roadpilot says that a speeding endorsement will remain on a driver's licence for four years, meaning that, over the period in which they are obliged to declare the conviction to insurers, it will cost the average driver a minimum of £420.

For male and female drivers with six penalty points, insurance premiums increase on average by 29.3 and 28.8 per cent, respectively. These figures actually represent a small decrease in the average price hikes compared to those surveyed in December 2011. However, three in 10 insurers now refuse to cover the driver (both male and female), as opposed to all 10 insurers agreeing to offer cover six months ago.

Why points are more costly now than six months ago is unclear – but then everything to do with car insurance is pretty opaque.