The windows at Parliament House have undergone extensive cleaning in recent weeks

Sunlight is literally permeating the home of Australia's democracy like never before.

Figuratively, though, the government is as opaque as ever — especially the department tasked with running Parliament House.

The Department of Parliamentary Services (DPS) can live in the shadows because of laws Anthony Albanese introduced in 2013, when he was the leader of the House of Representatives.

At the time, the parliament was concerned correspondence between politicians and the parliament's library could be released under Freedom of Information (FOI) laws, so an exemption was offered to the four parliamentary departments.

It was only meant to be an "interim measure" — pending a broader review — so it's no wonder transparency advocates said they were "startled" when it was revealed this week that the exemption remains on the books more than a decade later.

It leaves the DPS in rare public service air, where the only documents it releases to the public are those the department deems appropriate.

According to its critics, the DPS has largely been overlooked in the reckoning within Parliament House in the years after Brittany Higgins alleged, she was raped in a ministerial office.

But when the boss of the department, Rob Stefanic, fronted Senate estimates this week, it was relations closer to home that became the focus.

Stefanic initially told senators he wouldn't answer questions about his private life or what he described as the "elephant in the room" — whether or not he had been in a relationship with his deputy, Cate Saunders.

If there's one thing senators love at estimates, its highly paid public servants telling them they won't be answering their questions.

The senators — especially One Nation's Malcolm Roberts — were unperturbed. It made for several agonizing exchanges, some of which had almost a minute of silence before Stefanic responded.

Stefanic eventually denied that he and Saunders had a relationship while he was her boss but refused to answer questions about whether there'd been a relationship at any other time.

It ultimately fell to the new deputy secretary — Jaala Hinchcliffe, who joined the DPS from the national anti-corruption body — to explain why the department paid Saunders more than $315,000 as an incentive to retire payment while she was on secondment at Services Australia.

Liberal Jane Hume told DPS officials that Saunders had been given an "incentive to retire at an unusually young age" before suggesting it was a "highly unusual circumstance".

It was only on Thursday, when the Public Service Commissioner appeared at Senate estimates, that a more fulsome picture emerged.