Michael Martin had backed the Laois/Offaly TD Yesterday Afternoon.
The Taoseach's set to appoint a new Agriculture Minister today, after Barry Cowen was sacked last night.
It followed Mr Cowen's refusal to provide further public statements on allegations he attempted to avoid a garda checkpoint in 2016.
He admitted he was caught drink driving, but strongly denies trying to evade gardaí.
In a statement, the Offaly TD says the decision to sack him was surprising and disappointing.
Sinn Féin's Health spokesman David Cullinane says the Taoiseach needs to fully explain why his position flipped yesterday:
Eurovision Participation Decisions Come Down To Money And Audience - Eurovision Author
Fiosrú Finds Gardaí Acted Lawfully Before Fatal M9 Crash
EU Agricultural Commissioner "Blown Away" By Ploughing - Anna Marie McHugh
HSE Accused Of Withholding Home Support Data With 5,600 On Waiting Lists
Over 27,500 Midlands Drivers Could Pay Hundreds More For Car Insurance
Midlands Set For A Night Of Culture And Creativity
Westmeath Family Banned From Social Media Following Alleged Violent Incident
Laois TD Raises Concerns Over Lengthy Reserve Defence Forces Recruitment Process