GMTV presenter Eamonn Holmes is to step down from the breakfast television station after 12 years.
Holmes and Phillips have worked together since 1996
The 45-year-old Belfast-born presenter said it had been a "huge privilege" to work for GMTV since it first went on air in January 1993.
But he added that increasing radio and television commitments and business opportunities had led to his decision.
Holmes will remain on the sofa with Fiona Phillips until the end of April, when his contract is due to end.
As well as GMTV, Holmes also presents the BBC One show the National Lottery Jet Set, has his own Saturday morning show on Radio Five Live and writes a newspaper column.
He said: "It has been a huge privilege over 13 years to be invited into people's homes as host of such a high-profile daily current affairs programme, covering every major event in that time.
"However, with the opportunities that have sprung from GMTV has come an ever-increasing workload, the only way to make space is to step down from GMTV."
Holmes added that it was particularly difficult to end his partnership with Phillips.
"I'll particularly miss my partnership with Fiona Phillips and I wish her and all the rest of the team the very best for the future."
Phillips said: "This is our ninth year together - in fact, I have spent more time with Eamonn than I have with my own husband. I will miss him more than words can say."
GMTV managing director Paul Corley said: "We will miss him greatly and we wish him the very best for the future."