Parades cost the police in Northern Ireland £6.7 million last year, the Government revealed.
Disorder in Belfast over a three-day period in July resulted in the injury of 25 police officers, Northern Ireland Secretary Theresa Villiers said.
She said the Government would not tolerate violence.
"The strain policing the parading season places on PSNI resources should not be ignored, with PSNI figures estimating the total cost to them of this year's season at £6.7 million.
"There remains much to be done across the community to deal with instability caused by issues such as flags and parades."
She applauded the efforts of all of those who worked together to ensure that the vast majority of parades across Northern Ireland were peaceful during 2015.
"While it is encouraging that we have not returned to the level of violence seen in 2013, it remains a matter of significant concern that disorder in Belfast over a three day period in July resulted in the injury of 25 police officers.
"This is completely unacceptable. In the same month, a rogue group of loyalists made a public statement to the media threatening PSNI officers and the Parades Commission. This too is unacceptable.
"This Government will not tolerate acts or threats of violence by any part of the Northern Ireland community."
Stormont House Agreement plans for a commission to examine the thorny issues of flags, identity, culture and tradition are to proceed following November's political deal.
So too will a plan to transfer from Westminster to the Assembly the responsibility for regulating parades. An Executive discussion paper will be produced to outline options on how to regulate parades and associated protests.
PSNI assistant chief constable Stephen Martin said: "The annual cost of policing the Northern Ireland parading season remains a necessary expenditure for PSNI.
"It is our responsibility to ensure that the potential for serious disorder is minimised and that peace is maintained throughout parading events.
"Until we as a society can reach a point in time when serious disorder and violence are no longer a possibility, police will continue to be obliged to allocate significant resources to policing parades and associated events."