Specifically, the Military Police Complaints Commission says there remain "significant gaps" in its power to pry documents out of the federal government when conducting a public hearing or investigation.
The commission's annual report was tabled Monday in Parliament.
Fighting with the Harper government over access to documents figured prominently in two high-profile cases over the last few years, including the protracted fight over allegations of torture involving Afghan prisoners.
The government's refusal to hand over all of the records sparked a showdown in Parliament that almost defeated the Conservatives, who at the time governed with a minority.
The second case involved the refusal of National Defence to release documents related to the suicide of an Afghan veteran in 2007.
An independent review of the commission's mandate and activities last year recommended a series of changes, but legislative changes as part of the government's massive Bill C-25 did not go far enough, according to the annual report.
"Unfortunately, the commission s most vital proposals aimed at improving its capacity to address complaints efficiently and credibly notably, the need to enhance its authority to obtain relevant information were effectively not addressed," the report said.
"As these changes are necessary for the commission to properly discharge the mandate which Parliament has given it, the commission will continue to pursue them."
The bill was passed in June last year.
Jay Paxton, a spokesman for Defence Minister Peter MacKay, said the government "remains committed to co-operating with the (commission) to the fullest extent possible, consistent with (its) mandate" under the National Defence Act.
The government has a duty to safeguard certain information, he added.
"The obligation to maintain the confidentiality of solicitor-client communications is one of the highest ethical duties of lawyers and is a core provision of the codes of professional conduct of every law society in Canada," said Paxton.
"For reasons of public policy, it is extremely rare that it is waived and Parliament has unequivocally expressed its intent that the (commission) can and should accomplish its mandate without access to privileged information."
But NDP defence critic Jack Harris said the commission should not have to fight for every scrap of information it needs from the government.
He committed the party to implementing the requested changes, if New Democrats form government after the next election in 2015.
The commission's annual report also repeated the concerns of commission chairman Glenn Stannard, who voiced objection before a parliamentary committee in February over the legislative overhaul of the military justice system.
He told the Commons defence committee that Bill C-15 went against a two-decade trend of making military police more independent.
Of particular concern to Stannard was a provision in the legislation that allowed the vice chief of defence staff to "issue instructions or guidelines in writing in respect of a particular investigation" to Canada's top military policeman, the provost marshal.
He said that aspect was inconsistent with the changes made following the Somalia scandal of the 1990s, when it was felt that military police should have more independence to investigate possible wrongdoing on the part of senior officers, or the command.
Critics said the changes could allow the vice chief of defence staff to interfere in an investigation.
Bill C-15 is currently before the Senate, awaiting approval.
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