While stopping short of actually calling on her S&D group colleagues to reject Hogan, Childers warns in a letter seen by the Parliament Magazine dated 1 September, that appointing someone with Hogan's profile would, "send a very ominous signal to those who suffer and fight discrimination".
Childers' concerns centre on Hogan's actions last year when the Irish environment minister wrote to local councillors in Kilkenny in a bid to prevent a Traveller family from being provided with social housing following requests from residents for Hogan to intervene.
Hogan subsequently replied to local residents that the Traveller family, "will not be allocated the house in your area" and that he was "glad to be of assistance in this matter".
Hogan's intervention caused some media controversy at the time, despite the fact that local officials ignored his request and placed the family anyway, with accusations by Irish Traveller and Roma groups that the minister was, "pandering to prejudice" against Ireland's Traveller community.
"I must bring to your attention facts which were confirmed and defended by Mr Hogan himself. These, I believe, are incompatible with the proper discharge of the duties incumbent upon a European commissioner" - Nessa Childers
Widely known in Ireland as "Big Phil", Hogan is a leading figure in current Taoiseach Enda Kenny's government and a formidable political personality within the centre-right Fine Gael party.
In her letter, Childers says, "I harbour serious reservations concerning Mr Hogan's suitability to be a member of the college of commissioners, at the helm of the European Union's executive body".
"While my views, as an S&D member, and those of Mr Hogan, as a member of an EPP affiliated party, naturally differ, and while I take serious issue with instances of his personal past behaviour, those are, of course, not the reasons why I am writing to you, questioning Mr Hogan's suitability as a candidate to the commissioner's post.
"However, as a representative of all Irish citizens, including ethnic minorities such as the Traveller community, I must bring to your attention facts which were confirmed and defended by Mr Hogan himself. These, I believe, are incompatible with the proper discharge of the duties incumbent upon a European commissioner.
"Tragically, the family home provided in this specific instance… was subsequently burned down with most of their belongings. In an environment where intolerance can reach such extremes against the Traveller community, Mr Hogan's misjudgment in his capacity as a minister, which was roundly condemned across the opposition benches, proves all the more flagrant.
Childers adds that in her view, appointing Hogan would "send a very ominous signal to those who suffer and fight discrimination in Europe, on ethnic and on other grounds".
"We must show zero tolerance against racism, especially at a time when the far-right is once more raising its ugly head across the continent" - Nessa Childers
"I have no doubt that those would see this as a step backwards for equality. We must show zero tolerance against racism, especially at a time when the far-right is once more raising its ugly head across the continent."