Attorney-General George Brandis has described warnings from the journalists' union that new metadata laws are an attack on press freedom as "outrageous hyperbole".

Senator Brandis said the legislation would instead introduce new privacy protections and safeguards.

The metadata laws will require telecommunications companies to retain customers' phone and computer metadata for two years — something most telcos already do but with no mandated retention time.

The Government is hoping Parliament will pass the laws by the end of next week, after agreeing to a late request from Labor that a specific protection for journalists be included.

The compromise gives journalists what Senator Brandis described as a "limited exemption", in that agencies seeking to access journalists' phone and internet records would need a warrant.

But the Media Entertainment and Arts Alliance (MEAA) argues the amendment does not honour journalists' rights to protect their sources.

The union said the laws could deter whistleblowers and prevent important information ever coming to light.

"Accessing metadata to hunt down journalists' sources, regardless of the procedures used, threatens press freedom and democracy," MEAA chief executive officer Paul Murphy said in a statement.

The Attorney-General said the law has always recognised that protection of journalists' sources should be acknowledged.

"That is outrageous hyperbole," he said of the MEAA concerns.

"This law does not change the status quo, that's the first point to be made."

Senator Brandis said the Labor amendment was not necessary, but the Government would agree to it to "put minds to rest".

"At heart, all this legislation does is to mandate the continuation of the status quo," he said.

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"But it also builds in new protections, new privacy protections that weren't there in, aren't part of the existing law."

Senator Brandis outlined that the number of agencies that could access the metadata had been limited from 80 to about 20 and that the legislation would give the Commonwealth Ombudsman a new oversight power.

Also key to the new amendment is how it will define a "journalist" — Senator Brandis said bloggers would not be covered.

"There is an interesting argument of course, as to what at the margins a journalist is," he said.

"Ultimately that is an issue resolvable by courts."

The Opposition has declared the deal a "victory for journalists" but the measure is not without its opponents in Labor ranks.

While Opposition MPs formally agreed to support the metadata legislation in a Caucus vote this morning, the debate featured 15 speakers, with some raising concerns about the cost, effectiveness and oversight provisions in the broader legislation.

Another MP raised the murder of Melbourne woman Jill Meagher, whose case was solved using metadata.