Department of Parliamentary Services Secretary Carol Mills clashed with a Senate Estimates committee on Monday morning, saying she was denied natural justice by the Senate Privileges Committee which relied on dodgy advice from her bitter rival, Clerk of the Senate Rosemary Laing.

Labor senators said they were outraged on Monday morning by Ms Mills' defiance, with senior frontbencher Penny Wong and her colleague Joe Ludwig making it clear in a tense session that they wanted the senior public servant's resignation.

The Senate Privileges Committee said Ms Mills was guilty of "a serious breach of accountability and probity" and had misled an earlier estimates hearing about her conduct in the CCTV affair.

The row has been rumbling on since May 2014 when former Labor Senator John Faulkner claimed the department used Parliament House's CCTV system to spy on one of its employees.

But Ms Mills came out swinging at Monday morning's estimates hearing, telling Senators that no breach of protocol had been committed and expert advice from the Australian Government Solicitors' office, that should have been considered, was rejected by the Privileges Committee.

The DPS boss complained that the committee relied instead on advice from Dr Laing, who has been embroiled in in an increasingly bitter feud with Ms Mills.

"Further expert advice from the [Australian Government Solicitor] makes clear, however that advice from the Clerk of the Senate, upon which the Privileges Committee relied, is mistaken in a large number of areas, yet the clerk's advice had a significant impact on the final report," Ms Mills said.

The secretary also told the senators she had been denied due process and natural justice by not being given an opportunity to respond to the Privileges Committee's report before it was made public.

"The Privileges Committee did not follow their own resolutions in making adverse findings against me, as a result I was denied natural justice," she said.

"I do not believe I committed the errors that were found and suggested in the report."

Senator Faulkner believed the building's closed-circuit cameras were being used to spy on a DPS public servant who was acting as a whistleblower and supplying information to his office.

But Ms Mills said on Monday that the public servant, who has since taken a redundancy from the department, was being monitored because of suspicions they were in the building to harass a co-worker.

Senators Wong and Ludwig pressed their attack on Ms Mills, with the Queensland Senator saying it was inappropriate for Ms Mills to uses Estimates to defend herself.

"I think it's outrageous," Senator Ludwig said.

"If the Privileges Committee is going to be subject to attack by Ms Mills in this way, then I am concerned about it."

Senator Wong wanted to know why Ms Mills had not resigned after the Privileges Committee delivered its findings.

"How is it tenable for you to continue in the face of findings that you misled a Senate Committee?" the Labor frontbencher asked.