Ulster Unionist leader Tom Elliott has rounded on internal critics in his party, using a keynote speech to promise tough discipline.
He told the party's Annual General Meeting in Belfast, however, that it had not polled as well as he had hoped in the recent elections.
And in the wake of the loss of two Assembly seats, plus a poor showing in the contest for council positions, he said the party must reflect on criticisms of its structures and its failure to send a coherent message to voters.
"Let's be honest, if the media are saying that our message is mixed then maybe we should heed their opinion," he said.
"Maybe we should be doing everything we can to ensure that we speak with one voice.
"Maybe we should be doing everything we can to ensure that different members of this party aren't saying different things when they get before a microphone or camera."
He added: "So let me make something quite clear. I will hold to account any member of this party, be it an elected representative or an ordinary grassroots member, who thinks that they have the right to pursue their own agenda and damage the party."
The Fermanagh MLA said: "If you genuinely cannot live with a particular policy then consider your position.
"But I will not tolerate a situation in which someone uses the media to undermine me, undermine party policy or undermine the party itself.
"Ladies and gentlemen, those days are gone."