At The Races insisted "no material impact on ATR's profitability is expected" after it was announced Ascot is to switch broadcaster to Racing UK from the start of the 2014 Royal meeting.
Racecourse Media Group-owned Racing UK are responsible for the majority of Britain's major racecourses, including Cheltenham and Newmarket, and Ascot has decided to follow suit.
At The Races, which has exclusive rights to racing in Ireland, lost Exeter, Kelso and Perth to its rivals earlier this year and Folkestone and Hereford will also be missing from next year's line-up as both racecourses will shortly close down.
Ascot officially joins the Racecourse Media Group on June 12, 2014.
A statement posted on the At The Races website read: "At The Races is naturally disappointed that Ascot has chosen not to continue its relationship with the company from June 2014, a relationship which goes back to 2004 and which has at all times been conducted on the best of terms.
"No material impact on ATR's profitability is expected as a result of this decision as the company's revenue lines continue to grow and diversify."