MIKE Nesbitt described it as “a bad 24 hours for the image of unionism”.
The Ulster Unionist leader was responding to weekend violence in Belfast and south Antrim.
On Saturday, violent clashes between flag protestors and nationalists in east Belfast left 29 police officers injured.
The disorder followed attacks on the police in Newtownabbey and Carrickfergus the night before when vehicles were hijacked and set on fire.
It was the 40th day of street protests since Belfast City Council voted to restrict the flying of the Union Flag to 18 designated days only.
Mr Nesbitt said: “Images of burning vehicles, petrol bombs being thrown at the police, and people who carry the Union Flag but mask their faces have nothing to do with my vision of being British.
“On Thursday, politicians and community activists offered a positive alternative to what has been happening since December 3, namely a Unionist Forum.
“I urge everyone who cares about the Union to give it some time and space to explore its potential.
“Street violence from so-called unionists, no matter what age, advances nothing but the cause of Irish nationalism. It is high time those involved in rioting realised they are destroying the very cause they hope to promote.”
Almost 100 officers have been injured and more than 100 arrests made during six weeks of sporadic trouble.
On Saturday, up to 1,000 loyalists held a city centre demonstration against the council’s decision before a large section of the crowd then made their way back towards the east of the city.
Although the main protest passed off peacefully, tensions rose considerably when police blocked the Queen’s Bridge, preventing access to the shortest route to the Newtownards Road.
According to the PSNI, police were engaging with protest marshals as the main body of protestors broke away towards East Bridge Street – many now covering their faces as they passed Central Station and approached the junction with the nationalist Mountpottinger Road.
Several bottles and other missiles were thrown at the flag protestors by a crowd of masked nationalists from the Mountpottinger area. The confrontation led to further missile throwing from both sides, quickly followed by a brief episode of hand-to-hand fighting.
In the disorder that followed, police used water cannon and fired six baton rounds as the rival factions were forced apart. Four injured officers required hospital treatment, and two have since been released.
A number of properties were damaged in the Short Strand.
Chief Constable Matt Baggott described the protest and its aftermath as a “difficult operation” considering the “large number of people determined to cause disorder and violence”.
“My colleagues brought the situation under control with exceptional courage and professionalism. I know the vast majority of people will be grateful for their efforts. Police will continue to engage with all those committed to finding a solution to these issues,” he said.
Businesses in Belfast’s city centre have struggled to cope, with many reporting lost trade, and the Confederation of British Industry (CBI) warned some investors may think again.
Senior politicians from Belfast, Dublin and London are to meet in coming days to discuss the protests.
First Minister Peter Robinson condemned those responsible for the injuring of police officers but said protestors felt alienated.
The DUP leader said: “The only way forward is through the political process that has been endorsed overwhelmingly by the people in Northern Ireland.
“It won’t change anything to be involved in violence.”
Slamming the violent scenes near the Short Strand, SDLP MLA Conall McDevitt said: “Not content with last night’s chaos, today (Saturday) elements of an illegal parade broke away from a safe route home with no purpose other than to maximise sectarian tensions in an interface area.
“This violence was the preferred outcome of a significant number of people taking part in the march.
“There is also continued violent action against police officers, which perpetrators are attempting to legitimise on social media because of the presence of Catholics and southerners in the service.
“This is no legitimacy – this is a craven attempt at the most vicious, barbaric mob rule undertaken by those with no motivation except the destruction of any progress towards a truly shared society.”
Alliance East Belfast MLA Judith Cochrane said the flag protests and the violence were doing “untold damage to traders and businesses and Northern Ireland’s image is being tarnished”.
Meanwhile, a 32-year-old female has been charged with disorderly behaviour and obstructing a constable.
The woman is expected to appear before Belfast Magistrates’ Court today.
It is understood the charges relate to public disorder in the Castlereagh Street area of east Belfast on Saturday.