Provisional figures released today have shown that 527 people took their own lives during 2009, a 24% increase on the previous year.
In response to the new figures, the highest ever recorded in Ireland, the Government is to provide an additional €1m to fund to a range of suicide prevention measures.
The HSE says the dramatic change in the number of suicides reflects an international trend, where suicide numbers increase during periods of economic downturn.
The figures confirm a reversal of a downward trend between 2005 and 2008, when the number of suicides fell by 11%.
The HSE National Office for Suicide Prevention says it spent €5.6m last year on more than 30 projects - one of which, "letsomeoneknow.ie", designed for 13 to 17 year olds, received 26,000 hits.
In a statement, the HSE has stressed the importance of encouraging people to talk with friends, relatives or a health professional if they are experiencing difficulties.
The Samaritans can be contacted on 1850 60 90 90.