The Canberra Times can reveal the precarious state of the hospital's books was caused by a budget overrun that saw the northside health facility deliver a "disappointing" financial performance last year.

It is understood the trouble stemmed from the hospital overestimating its cashflow.

Despite this, the hospital wants the government to help fund an extra 200 beds, according to Calvary Health Care ACT's 2014 financial report.

Although the hospital is under financial pressure, it is believed no jobs are at risk, however, a temporary staff freeze has been introduced.

The financial report indicates the hospital lost $4.9 million last year, which is nearly a $6 million turnaround on the previous year's $1.1 million surplus.

This was despite the hospital's revenue increasing $11 million from $218.7 million in 2012-13 to $230.2million last year.

The report revealed 85 per cent of revenue from operating activities came from government grants and subsidies and totalled $190.8 million last year, up from $181.3 million the previous year.

The hospital's financial woes are believed to have been caused by service delivery costs blowing out beyond the funds allocated.

But Mark Doran, national chief executive officer of Little Company of Mary Health Care, said Calvary had absorbed the "budget overrun" and made assurances the bill would not be footed by ACT taxpayers or the government.

"The disappointing financial performance of Calvary Health Care Bruce last year is something we are actively working to address and we remain committed to the provision of safe, effective and high quality health services to our community," he said in a statement.

"We are keeping ACT Health closely informed about all aspects of this issue."

Mr Doran said the "obvious and immediate" challenge was to meet activity targets set by the government under budget allocations, but he was confident this could be done.

Chief Minister Katy Gallagher was aware issues about Calvary's financial performance had been raised with the government and was confident the steps taken by the hospital's operator to investigate were appropriate.

Opposition leader Jeremy Hanson said the Canberra Liberals would investigate the hospital's financial stress further and seek assurances it would not impact the treatment of public hospital patients.

"Back in 2009, (former ACT Labor leader) Wayne Berry came out and said words to the effect of that Calvary should be left to wither and die, now I would hope the financial stress that Calvary is experiencing is not as a result of sections of the Labor party who want to see Calvary wither and die," he said.

A plan for the government to buy Calvary from its operator, Little Company of Mary, for $77 million and to spend $200 million on a much-needed upgrade collapsed in 2010.

Mr Doran said Calvary's partnership with the ACT government and relationship with ACT Health remained strong.

He said despite the hospital's "disappointing financial outcome" in 2013-14, several new services had been opened in that time.

The hospital also recently lost its chief financial officer Wayne Armistead and chief executive Ray Dennis while the hospital's nursing and midwifery chief left to take a senior position in Queensland and be closer to her family.