Career
Costelloe was from Ballyduff, Tralee, County Kerry. He was nominated as a candidate to the Industrial and Commercial Panel of the Seanad by the Taoiseach, Sean Lemass following the death of Fianna Fáil senator Daniel Moloney. Writing in The Irish Times under the pseudonym Backbencher, journalist John Healy claimed that Costelloe"s election was due to the "Kerry Mafia" in the Fianna Fáil party who had insisted that Moloney, a Kerry native, should be replaced by someone from the same area.
Healy, suggesting Costelloe was older than his claimed age of 63, and was poorly qualified for the Industrial and Commercial panel ("He runs a tidy little grocery shop and he has a bit of land"), pointed out that he had previously failed to be elected to Kerry County Council, and suggested Costelloe would have little to contribute in the Seanad ("he will cause the shorthand takers no trouble").
In the event, he made just four interventions during his term. He was not re-elected at the 1965 Seanad election.
