I have a UK tourist visa for 6 months. Am currently in the UK and my visa is about to expire.I have decided to stay in the UK for at least year. Can i renew my visa before it expires while in UK?
No, you may not extend your tourist Visa for any period longer than 6 months. The maximum allowed is 6 months. If your original Visa was shorter than 6 months, then you could apply for an extension up to 6 months from your date of arrival. But in your case, your six months are almost over and your Visa was for 6 months.
See here for more information.