free vote 
noun chiefly British
A parliamentary division in which members vote according to their own beliefs rather than following a party policy: MPs were allowed a free vote on the issue...
- He also said it was the right decision to give party members a free vote, because the issue was a deeply personal one.
- However, he has repeatedly said he would allow free votes on private members' bills on any issue.
- Further, all political parties should allow a free vote on the bill according to a legislator's conscience.