Seasonal pressure on hospital emergency departments has been particularly severe in 2013 and this has put pressure on waiting lists, according to the HSE's latest performance report.

The report says responding to this pressure by increasing hospital capacity has been one of the factors in the HSE running up a deficit of nearly €25 million to the end of April.

The number of patients waiting over six months for hospital treatment has nearly doubled since the end of last year, the most recent figures from the Deartment of Health show.

The HSE, in its performance report for April, said the scale of the impact on waiting lists has been particularly noticeable in the Mater, University College Hospital Galway, Beaumont, Cork University Hospital, Limerick Regional Hospital Dooradoyle, and Our Lady's Children's Hospital Crumlin.

It says the usual seasonal 'winter' pressure on EDs has lasted longer than expected and has put pressure on beds for non-emergency patients.

An intervention plan including site visits, specialty and procedure reviews, clearance plans, targeted spending of a national intervention fund and intensive performance management has been taken place to deal with the pressure on planned procedures.

The HSE and the Department of Health have planned that no adult will be waiting longer then eight months for a planned procedure by theend of this year.

The HSE report says just under 100,500 patients are currently waiting over a year for an outpatient appointment in a public hospital. The target is to have no patient waiting longer than a year for an outpatient consultation by the end of the year.

The report says just over one fifth of ED patients currently have to wait over nine hours to be admitted or discharged.

According to the performance report, the significant and extended ED pressures on services in the first four months of the year which have required the HSE to respond, including with additional capacity, has had 'an impact to-date on our costs as well as on our ability to fully sustain the very important improvements made last year including in access times to scheduled care.'