If you think that it is favouritism, rather than something like your sex, race, religion, disability, sexual orientation, (for example) then I doubt that you would be able to claim under discrimination legislation.
Favouritism in itself is not unlawful.
Not knowing enough about your situation it IS possible that you may have a claim for Equal Pay if you are doing the same work, or work of equal value, as the " favourite".
If you are having money held back, then you could take it up through the grievance procedure / see HR about it.
If you think that the manager is bullying or harassing you, then your workplace should have a procedure on this, and you should be able to take it up through HR.
Sacking you for raising a grievance would be potentially unfair dismissal. Making your life a misery, and causing you to leave through bullying, or because you raised a complaint, potentially could be seen as constructive dismissal.
Are you in a trades union?