Loyalist protests which left hundreds of police injured risk running out of control, the top policeman in Northern Ireland said.
Relationships may be being poisoned by nightly rioting, potentially damaging key political talks this month aimed at resolving tensions over parading and flags, Police Service of Northern Ireland (PSNI) chief constable Matt Baggott warned.
Just under 700 officers have been injured in the last year policing public order - attacked with petrol bombs, scaffolding, bricks and swords - and costs are reaching the highest on record, a meeting on policing in Belfast heard.
Mr Baggott said: “The protest is in danger of running out of control. It is important we give (US diplomat) Richard Haass every opportunity to do his work because that protest runs the risk of poisoning relationships.
“This protest can be dignified but at the moment everybody is a loser and possibly for a long time.”
More than £15 million has been spent since April on policing parades, protests and associated disorder, police said. A total of £14 million was used over a 21-day period in July - £2.3 million on the Twelfth alone.
Police said 689 officers have been injured since July last year, and 18 remain on sick leave.
A troubled marching season last summer was followed by loyalist protests against a Belfast City Council decision to restrict the flying of the Union Flag from the city hall. Weeks of intense rioting followed, and hand-to-hand sectarian fighting between Catholics and Protestants briefly erupted in East Belfast.
This summer, fresh violence occurred following restrictions placed on a loyal order parade through North Belfast and after a march through East Belfast.
Days of rioting took place, the Sinn Fein lord mayor of Belfast was attacked by an angry crowd and there are still protests in North Belfast.
PSNI assistant chief constable Will Kerr said: “The journey between normality and crisis in Northern Ireland is only about 24 hours because there is an inherent unpredictability of very large numbers of people at an interface and we need a solution to come very quickly.”
Mr Baggott told the Policing Board, which scrutinises the police, of real long-term pressures on the PSNI, with the trouble taking officers away from normal duties.
“(These are) not just about greater public expectations, new responsibilities such as sex offender monitoring, policing the internet or the past, but are about dealing with very serious issues of public order, terrorism or international crime that could rapidly undermine stability and hope for the future,” he said.
He added that policing numbers, which have been reduced following the end of IRA and loyalist violence in the 1990s, should not fall below 7,000.
US diplomat Richard Hass is to chair all-party talks this month aimed at addressing issues about dealing with the past, parades and protests.
Police said 19 officers sustained more serious injuries during the violence, including fractures and dislocations.
Mr Baggott added: “There are real consequences to these protests which are damaging all communities. We cannot tackle the scourge of drugs, anti-social behaviour or even child exploitation when people are holding the line night after night.”
Democratic Unionist board representative Jonathan Craig said loyalist communities held the perception that representatives of their community were treated differently by the police, an allegation the force rejected.