If you literally only want it for public liability then I guess so - maybe just compare the policy wielding for what circumstances they would pay out under. Also check there is nothing on your household insurance policy that wouldn't already cover you - sometimes they have unexpected add-ons included.
What's the reason that you want to have liability insurance? Do you ride a lot or take a part in competitions? If I was to pop out for a bike ride and crash into your car, causing damage to the vehicle, it's highly likely that the public liability part of home contents insurance will cover you against any claim for accidental damage – but only if you're a cycling enthusiast as opposed to a serious hobbyist. But you can also take out third party insurance to protect against collisions where you injure someone else or damage their property and some insurance companies offer third party insurance as part of their theft insurance policy. Personally I'm poor in cycling, I don't have such insurance. But my sister in California is a professional biker and she even won a race one time. She has such insurance in www.mis-insurance.com/ It costs her a lot but she really needs it.
We donate to the Cyclists Defence Fund since the rebranding of the CTC. I seem to remember that some sort of legal expenses cover was included in the old CTC but it isn't anymore. I think that the CDF funding has altered (in a bad way).
I am not sure how you would check which insurers offer third party liability cover without checking each one but it is worth considering a legal expenses extension if you do.