Chief Constable Jon Boutcher has said the policing operation over the Drumcree parading dispute has cost about £3m so far.

Speaking at a meeting of the Policing Board, he described the situation as "challenging" - but said that despite "very significant tensions" there had been no violence.

The stand-off - over a proposed Orange Orange parade in Portadown, opposed by nationalist residents of the Garvaghy Road - has lasted since Sunday morning.

The Police Service of Northern Ireland (PSNI) has deployed a significant number of officers, with Boutcher saying he had a responsibility to preserve peace and maintain order.

He said the cost of the policing operation has been £3m thus far, but warned of the consequences and cost "if they get it wrong".

"The consequences of us not getting this right, and the cost of that, the monetary cost of this organisation in having to police potential disorder, and the cost to the security, the safety, the trust, the confidence, the tranquillity of the society," he added.

During the meeting, it also emerged that the Policing Board has launched a code-of-conduct investigation into one of its members, Sinn Féin's Deirdre Hargey.

She was pictured taking part in an unlawful protest against the march on the Garvaghy Road on Sunday.

Hargey attended the board meeting after a failed attempt by Democratic Unionist Party (DUP) assembly member Trevor Clarke to have her barred.

"I've made it clear to my senior team that our objective is to facilitate the Parades Commission determination," said Boutcher.

"The Parades Commission determination means that the Orange Order can lawfully parade down the Garvaghy Road. Without that determination, such a parade would be unlawful.

"What it does not mean, however, is that the police must accommodate that determination at all costs."

He said the police were not expected to "nor will they force" members of the Orange Order "through a hostile crowd", saying it could be unsafe or have wider consequences for Northern Ireland which could be "catastrophic".

With the PSNI currently being unable to police the Parades Commission ruling to allow the march, Boutcher said he was giving "space" for negotiations.

Under legislation, he can apply to the Northern Ireland secretary to have the determination overturned or amended.

Boutcher said: "The board needs to be reassured that I am constantly reviewing that position.

"But at this stage it is my judgement that that is not necessary.

"We are creating the time to resolve this and that is in the interests of everyone."

He said the investigation into the unlawful protest, which prevented the parade, was underway and was "fully resourced".

Boutcher said potential offences included unnotified protest, obstructing a lawful parade and breaching the Parades Commission determination.

"Believe me, the evidence gathering process has been extensive," he said.

"I want it to be thorough but I want it to be expeditious to send a clear message.

"The rule of law will come through."

Last Friday, the Parades Commission said the Orange Order's march could go ahead along Garvaghy Road.

Rather than start at 13:00 on Sunday as intended, the commission said it could begin no later than 08:00 and with 35 participants rather than the 60 the Orange Order requested.

But an initial legal challenge from the Garvaghy Road Residents' Coalition (GRRC) at the High Court saw a judge issue an injunction banning the parade, with Judge Patricia Smyth saying the "long-running dispute has the potential to escalate within Northern Ireland".

This was later successfully challenged by an Orange Order member at the Court of Appeal.

Late on Saturday evening, the GRRC was given permission to challenge that decision at the High Court - an appeal which was dismissed by Justice Humphreys.

The Drumcree parade dispute began in the mid-1990s and almost derailed the peace process at the time.

Violence related to the dispute resulted in riots, roadblocks and murders.

When the Orange Order was prevented by police from walking down the route in July 1995 there was a tense stand-off. It was the same for the next three years.

The Parades Commission began operating in 1998 to regulate parades and try to defuse tension around marches.

Its decision not to allow a march down the Garvaghy Road that summer has been challenged by the order - unsuccessfully - over the past three decades.