The report also found many federal politicians are not happy with the house's food, with just 40 per cent giving the catering a thumbs up.

The news comes in a difficult week for Ms Mills, who defended herself from damning attacks in Senate estimates from Labor Senators Penny Wong and Joe Ludwig who implied she should resign following a controversial report finding she had misled a parliamentary committee.

The attacks follow tensions last May when former Labor Senator John Faulkner's claimed the department used Parliament House's CCTV system to spy on one of its employees.

In change of managing Parliament House, the Australian National Audit Office found the majority of the department's contacts, covering such services as the building's catering, IT, cleaning, and security, were unable to show they were worth it.

"In developing contracts, many of which are long standing, around 40 per cent of those examined had business cases with clear value for money arguments," the report said.

Overspending on contracts was an "underlying problem" according to the auditors, singling out an industrial cleaning contract for critique.

"A further $183,731.02 has been spent with this contractor which has not been recorded against the [outline agreement]," the office said.

The audit office said there were "some issues were also evident around delays in payments."

Although it had demonstrated it had improved significantly since, the department came last in a group of 37 government agencies in the time taken to pay small businesses, according to a separate 2013-14 Treasury report.

The audit said DPS was "one of only two agencies that did not meet the benchmark of paying 90 percent of small business invoices on time" according to the Treasury report.

DPS paid 86.6 per cent of invoices to small businesses within the 30‐day payment period in 2013–14.

The audit also had problems with how department found out about and took action on bad contractors, with many lacking proper performance indicators.

"In one of the larger contracts, DPS relies on the contractor to report performance without the department having sufficient processes in place to verify data.

The report goes on to say that "systemic deficiencies in record keeping" give no guarantee that poor performing contractors would be found out.

With the report finding issue logs were used for less than a quarter of the contracts the looked at, the auditors calls for the department to do better.

"There were also instances where predominantly ad hoc oral communication provided little assurance or visibility of the contract's management or the quality of deliverables," the audit office said.

The auditors found some contracts were extended without good reason.

"For example in three of the contract extensions reviewed, documentation of reasons or justification for the extension did not cover aspects of contract performance, value for money, the financial impact of continuing the contract or the feasibility of going back to the market," the auditors said.

The report also included the result of a September 2014 survey of parliamentarians, which 33 contributed to.

The nation's politicians singled out the building's quality of food and drink for critique, and were also worried about the house's toilet supplies, dirty windows, the florist, and the department's handling of the building's heritage value.

It found, however, that 73 per cent were happy with DPS's management of services overall, with the highest rating of 70 per cent satisfaction going to parliament's library services.

The report also found high staff turnover in 2013-14 has had a "significant impact on staff morale and turnover".