Israel’s Environmental Protection Minister Avi Gabbay resigned from his post on Friday amid the recent addition of Avigdor Lieberman’s ultranationalist party to the coalition.

The resignation of Gabbay, a member of the centre Kulanu party, comes in the wake of recent appointment of Lieberman, a known hawk, as the defence minister. Gabbay in a statement said the nomination “undercuts Israel’s security”, Xinhua news agency reported.

Lieberman demanded the defence ministry portfolio in place of Moshe Ya’alon, a moderate member of Prime Minister Benjamin Netanyahu’s Likud party.

After Netanyahu received Lieberman’s request, Ya’alon resigned last week, saying the government has lost its ethical compass and he had lost his faith in Netanyahu.

“The recent political steps and the replacement of the defence minister are, in my eyes, a serious act that ignores what is best for the security of this state,” Gabbay said on Friday.

He also said the move will cause “greater polarisation” among the Israeli people and that he cannot be a partner, or serve any longer in the current government, amid Lieberman’s hardline stance.

Finance Minister Moshe Kahlon, who heads Gabbay’s Kulanu party, on Friday said he will seek to keep the environmental protection portfolio.

Last week, Orly Levy-Abekasis, a member of Lieberman’s Yisrael Beytenu (“Israel Our Home”) quit the party amid the coalition deal between Netanyahu and Lieberman, and will serve as an independent lawmaker in parliament.

Netanyahu and Lieberman signed a coalition agreement on Wednesday, as Netanyahu sought to expand his coalition, which only held a 61-59 lead over the opposition in parliament.

Other than the defence minister’s post, Lieberman also managed to secure increased pension stipends for migrants from the former Soviet Union.

About 1.6 million people migrated from the former Soviet Union to Israel between 1989 and 2006.