My housemate hasn’t been paying rent so would I get into any trouble were I to refuse to pay him bills until he does?

the bills are solely in his name, so I’m thinking of serving him with the ultimatum of i will pay him back for my share of the bills if and only if his rent if completely paid at the end of the tenancy? mostly cause if it isn’t I wouldn’t have the money to cover the debt if I don’t have the money I would have paid in bills (we’re on a joint tenancy) 

he has paid some back to the landlord since the rest of us found and and yelled at him (we had more luck with the landlord mostly because he has to live with us, he can avoid the landlord)

but just wondering if this puts me in a legally dodgy position later if I do this to make sure he keeps paying rent, obligatory question mark?