HSE chief Tony O'Brien has warned that the health executive could face a significant deficit again this year if planned cost-control measures are not implemented.

In his latest report to the HSE Board, the Director-General Designate said a core deficit of €11 million had already been run up at the end of March.

If temporary surpluses currently recorded by some services were excluded, the real deficit would rise to €33 million, he warned.

Mr O'Brien said this could give rise to a very significant level of deficit to year end.

He said the scale of the challenge in the HSE trying to break even by the end of the year 'remains very significant.' The HSE had to get a €360 million supplementary grant from the Department of Health last year to balance its books.

Mr O'Brien said the financial challenge would increase if there was an absence of continued and improved flexibility under the Croke Park Agreement.

His report notes that the HSE had budgeted for €150 million in savings this year under Croke Park 11, which was rejected by public service unions in March.

While attempts are being made to revive the deal, health unions are threatening industrial action if pay cuts are unilaterally imposed by the Government.

Mr O'Brien, in his report, stresses that anything that might jeopardise the flexibility which is available under the existing Croke Park 1 deal creates risks across most of the areas of cost containment set out in the HSE's national service plan for this year.

The report also shows that an extended flu outbreak and a high level of respiratory illness has put sustained pressure on emergency departments and on treatment waiting lists.

According to the report, there were 4,846 adults waiting over eight months for hospital treatment at the end of March, compared to 3,753 at the end of February.

There were 553 children waiting over five months for treatment at the end of March, compared to 447 at the end of February.

The HSE has set a target of having no adult waiting longer than eight months for treatment and no child waiting longer than five months by the end of the year.