[2] From 1973 to 1977, O'Mahony was a policy advisor to the Tánaiste and Minister for Health, Labour Party leader Brendan Corish.
O'Mahony himself stood unsuccessfully as a Labour candidate at the 1969 and 1973 general elections in the Dún Laoghaire and Rathdown constituency.
[1] In March 1983 he was appointed as a Member of the European Parliament, filling the vacancy caused by the resignation of John Horgan.
[7] As a lobbyist against plans for legislation to protect workers against passive smoking, O'Mahony was named in 1999 as having been involved in lobbying by ITMAC which Dr Fenton Howell, vice-president of the Irish Medical Organisation, claimed "secretly manipulated and misled a group advising the minister for health on new smoking regulations".
[8] After hearing O'Mahony's evidence, the chairman Batt O'Keeffe told Mahony that some of the points made about his conduct were "well-founded", and recommended that "in future deliberations he would be conscious of the public interest and people's health".