The pressure on Fianna Fáil party members to back a programme for government is 'a manufactured crisis', according to the party's TD Éamon Ó Cuív.
He has confirmed he will "absolutely" oppose the deal and questioned why it took so long for the leaders of the three parties to strike a deal.
Earlier, Taoiseach Leo Varadkar said there would be a political crisis if the memberships of each party didn't back the programme.
Speaking on The Hard Shoulder, Deputy Ó Cuív said: "I don't believe this was the Government the people voted for, I don't think it's where Fianna Fáil should be.
"The election made one thing clear: [people] were unhappy with the previous government.
"Fianna Fáil fought the election on the basis of a need for change, as did many other parties. The reality is over two elections Fine Gael have been defeated roundly twice."
He said he's been warning of the need for parties to "not be talking and talking and talking" since February, and that the parties have now been left in a "mess".
He argued: "There's a manufactured crisis now, because we are up against the wall in terms of renewing the Offences Against the State Act.
"The three party leaders have talked so long that they've actually made it difficult.
"One has to wonder why suddenly, at the last minute, they can do deal and then more or less say 'you can have the vote, but you do realise that the vote has to be one way'".
The Galway West TD suggested Sinn Féin will be among the few groups "smiling" after the deal agreed yesterday.
He explained: "The opposition party will grow - that's nearly inevitable.
"Since Sinn Féin are going to have 37 seats, and all the other smaller parties have six, the reality is they will be the people who will singly be the opposition party."
If the deal doesn't pass, Deputy Ó Cuív says he believes there's a high probability that President Higgins would exercise his power "to refuse the dissolution" of the Dáil and tell parties to try to find another arrangement.
He added that he 'doesn't want a general election in the middle of a pandemic', and that he doesn't believe such a prospect would be popular within Leinster House either.