He was elected to Dáil Éireann at the 1981 general election as a Fine Gael Teachta Dála (TD) for Dún Laoghaire and re-elected at the February 1982 and November 1982 general elections [REF].
In 2003, the Mahon Tribunal, set up to investigate allegations of corruption among Irish politicians, heard that Cosgrave had accepted illegal payments from property developers in return for voting to rezone property in Dublin.