"The lawmakers from Agreement will leave the caucus of the ruling Law and Justice (PiS) and will form a separate parliamentary group," Strzezek said after the Agreement board's morning sitting.
The move comes after Prime Minister Mateusz Morawiecki on Tuesday asked President Andrzej Duda to dismiss the head of the junior coalition partner, Jaroslaw Gowin, from the posts of deputy prime minister and minister of development, labour and technology.
This dismissal is the de facto breaking up of the governing coalition and the de facto end of the United Right, Gowin told reporters on Tuesday.
On Wednesday, Deputy Defence Minister Marcin Ociepa, hailing from Agreement, said he was also resigning from his post "in solidarity" with Gowin.
Radoslaw Fogiel, PIS deputy spokesperson, commenting on Agreement's Wednesday decision, said that PiS expects to retain a parliamentary majority after Gowin's dismissal.
"This is definitely not the end of the United Right, I am not worried about the majority in the Sejm (lower house)," Fogiel said, adding he hopes that some members of Agreement will continue to work with PiS.
But Fogiel did not rule out a minority government scenario.
"Obviously this is a realistic scenario... that sometimes happens in politics, not only in Poland. It is difficult, uncomfortable, to rule in such a situation but it is not impossible," he added.
The United Right coalition has been strained over Agreement's criticisms of tax reforms in the government's flagship Polish Deal economic programme.
Government spokesman Piotr Mueller said on Tuesday that Morawiecki had made his decision mainly due to "insufficient progress" made by the ministry headed by Gowin with the Polish Deal.
To date, twelve Agreement MPs have been part of PiS caucus, including five deputy ministers. (PAP)