The government is furious with the ABC over a new three-year pay deal with its employees that includes 2 per cent annual pay rises, a $500 sign on bonus, two weeks' extra paid parental leave and a new provision for domestic violence leave.

The government believes the deal is too generous given the state of the federal budget and the ABC's complaints about funding cuts over recent years.

Employment Minister Michaelia Cash wrote to the ABC in September to say it was "required to comply" with the government's tough workplace bargaining policy which disallows such benefits.

Senator Cash and Communications Minister Mitch Fifield wrote again last month to say it was "the government's expectation that the ABC would comply with the terms of the policy".

Australian Public Service Commissioner John Lloyd, in charge of enforcing the government's bargaining policy across the public service, last week said: "Ministers and myself have conveyed to the ABC's management our utmost concern at the position they have adopted in breaching the policy."

In a strongly-worded letter to Mr Lloyd posted to the ABC's website on Wednesday, Mr Spigelman said there was "no lawful basis" for the claim that the ABC was required to comply with the government's bargaining policy.

"Your assertion of authority to control the internal staffing policies of the ABC, potentially in any aspect of the wide-ranging powers conferred on you by the Public Service Act, is a fundamental challenge to the independence of the ABC from government interference," Mr Spigelman wrote in the letter, which was also sent to Senator Cash and Senator Fifield.

Mr Spigelman said it was the ABC board's "firm belief" that there is "no lawful requirement" to comply with the government's policy.

The ABC is merely required to consider the government's policy, he said.

"At all times in its bargaining on a new enterprise agreement, the ABC has sought an outcome that is fair and reasonable for staff while consistent with the board's responsibilities to deliver an efficient, effective and independent national broadcaster," he said.

Mr Spigelman said the ABC's attempts to modernise its workplace agreements had been "resisted" by unions and led to 26 weeks of "fruitless negotiations and the threat of industrial action". So management decided to bypass the unions and put its own offer to staff which was endorsed.

Mr Spigelman said it was misleading for Mr Lloyd to compare the ABC's pay and conditions with those at SBS given the multicultural broadcaster is subject to greater legislative control than the ABC.

Earlier this week Treasurer Scott Morrison said: "What I find strange about this is that every time we tell the ABC to tighten its belt they say that Peppa Pig has got to go off air, but when it comes to these sorts of arrangements they seem to be able to find the money."

The Australian Public Service Commission and Senator Fifield have been approached for comment.