Peter Robinson and Mike Nesbitt have both issued unequivocal appeals for the Union flag protests to stop – saying they will not lead to a U-turn on the decision taken by Belfast City Council.
The First Minister said protesters responsible for attacks on the police and violence were "doing a grave disservice to the cause they claim to espouse and are playing into the hands of those dissident groups who would seek to exploit every opportunity to further their terror aims".
UUP leader Nesbitt warned the on-going disruption would never lead to the Union flag returning to the mast at Belfast City Hall to fly all-year round.
As protesters plan to converge on the City Hall this afternoon, Mr Nesbitt warned this would be a futile gesture.
"I don't think anyone is going to look out the window of City Hall, see protests, and say, 'oh look at that, we had better put the flag back up'," he added.
DUP leader Mr Robinson also called for the protests to stop, saying: "Alternative political routes are available and a continuation of the protests has no role in changing the bad decision that was taken."
Last month the council voted to reduce flag flying to designated days despite unionist opposition. Mr Nesbitt conceded that, although he didn't like it, the vote constituted a democratic decision. "The only way to get the flag up again is to get a democratic vote that reverses the democratic vote that took it down. This has got to be a political decision," he said.
"I support the right to peaceful protest but after the attempted murder (of a policewoman) it seems to me that the risk of violence is now too high.
"I think the street protests have achieved all that they can achieve. That is basically raising awareness of a real depth of anger, not just over the flag vote but about the lack of a peace dividend and the political impasse between Peter Robinson and Martin McGuinness in the heart of Government."
Mr Nesbitt and Mr Robinson will meet on Monday to convene their Unionist Forum. However, the Ulster People's Forum, an alternative body set up to represent the flag protesters, has stated it will not be attending.
Both Mr Nesbitt and Mr Robinson expressed some sympathy with protesters' demands but condemned the tactics and called for a political way forward to be found.
Mr Robinson said: "While people are entitled to lawfully and peacefully protest, there can be absolutely no justification for issuing threats, acts of violence and terror or other unlawful behaviour."
At least 65 police officers have been injured by protesters since the row erupted when the flag was removed at the beginning of December.
"Those responsible are doing a grave disservice to the cause they claim to espouse and are playing into the hands of those dissident groups who would seek to exploit every opportunity to further their terror aims," the First Minister said.
Recalling that some protest spokesmen had called the police the "terrorist PSNI" and describe officers as "Nazis", he said: "This is language borrowed from the republican handbook."
He believed some protesters were using demonstrations as a means of attacking his party.
"Their attacks on the DUP expose their real target," he said. "It is not about the flag, the Alliance Party, Sinn Féin or the erosion of culture. It is a straight-forward politically motivated attempt to undermine the DUP as the voice of unionism despite our attempts to oppose the removal of the Union flag in Belfast."
He then lashed out at calls by "politically motivated spokespersons, who are to the fore in attacking the DUP" for a return to direct rule. He said that would be disastrous.
The DUP leader added: "This is the direct rule that left unionism powerless and put Sinn Féin in the driving seat."
He predicted that the return of direct rule "would lead to water charges for every household", as well as the introduction of "same sex marriages and abortion on demand on our community".