"I was asked, because I run the group of independent, non-partisan deputies, to accept her to the group since she is no longer in the HDZ group," Grubisic told reporters.
He said Kosor would not be able to defend in parliament on behalf of the group a political option that had not been agreed beforehand, adding that there would be no cooperation in terms of ideology or programmes.
Kosor was recently ousted from the strongest opposition party, the Croatian Democratic Union (HDZ).