Gordon Elliott has been banned from entering horses in UK races until an investigation into a photo from his yard is completed.
The Cullentra House trainer is said to be co-operating fully with an Irish Horse Racing Regulatory Board (IHRB) probe into a photo taken of him astride a dead horse.
In a statement on Sunday night, Elliott apologised "profoundly for any offence that this photo has caused and can categorically state that the welfare of each and every horse under my care is paramount".
Horse Racing Ireland on Monday strongly condemned "the disturbing photograph that appeared on social media".
The British Horseracing Authority (BHA) said earlier in the day, that the photo undermined the sport.
But Gigginstown House Stud owner Michael O'Leary said he will continue to support Elliott.
O'Leary - who enjoyed Cheltenham Gold Cup and Grand National success with the Meath trainer - said in a statement today that the "care and welfare of all our animals comes first".
But he adds that he believes it was a "momentary lapse of judgement" and that he accepts the apology.
Elliott trained four winners at Punchestown on Monday afternoon, but he will not be allowed repeat similar successes on UK soil.
The BHA have followed their original statement by saying, "The BHA, which regulates racing in Britain, will use powers under its own rules to refuse to allow horses trained by Mr Elliott to race in Britain pending consideration of the outcome of the Irish investigation".
The British Horseracing Authority (BHA) will not allow the Irish trainer Gordon Elliott to race horses in Britain whilst the Irish authorities investigate an image that appeared on social media over the weekend.
The trainer admitted the photo was genuine and apologised for his actions.
The BHA, which regulates racing in Britain, will use powers under its own rules to refuse to allow horses trained by Mr Elliott to race in Britain pending consideration of the outcome of the Irish investigation.
The action taken by the BHA recognises that Mr Elliott is licensed in Ireland, whose regulatory body, the IHRB, is carrying out its own investigation.
However, Mr Elliott has entered horses to race in Britain, from which point the British Rules of Racing apply to him.
The decision to refuse to allow horses trained by Mr Elliott to run in Britain is therefore an interim decision which the BHA regards as proportionate in these circumstances.
In an earlier statement, the BHA said it was appalled by the image which undermined its values of respecting and caring for horses.