How do I deal with 2 difficult girls?

In my group of friends at 6th form, there are 2 girls that I have difficulty with. One girl often criticises what Im saying to another person, and always talks to me in a monotone sarcastic manner. The other girl is far worse, whilst sometimes we share temporary good relations, she is incredibly overbearing. She thrives on arguments and confrontation, and always states that I'm in the wrong when I don't know what I've done. My parents got involed in one of these arguments once, and both girls have criticised me for it ever since. Both sometimes work together in their mind games and seem to be happy when they think they've insulted me. They both like to get the rest of my group of friends involved,in arguments and criticism against me, and seldom communicate with me when their on their own. I would like an ertive way in preventing what they're doing and stop it happening permanently. I am also worried that whatever I do will destroy my friendship with other people in my group