The rift between Prime Minister Benjamin Netanyahu and Gideon Saar, his most prominent critic within Likud, burst open this week in the aftermath of the escalation in Gaza.

On Monday, as it became evident that this round of violence had ended, Mr Saar said in an interview: “The ceasefire, in the circumstances in which it was reached, has no achievements for Israel. The periods between the rounds of violent attacks on Israel are getting shorter and in the meantime the terror organisations in Gaza are getting stronger.” He added that “the battle has not been prevented, just postponed.”

While similar criticism has hared from Likud members, sometimes even ministers,  it has until now been off the record or anonymous.

Mr Saar’s open criticism of the way the prime minister has handled the Gaza front is rare within Israel’s governing party, especially so soon after Mr Netanyahu’s fifth election victory last month.

The prime minister’s office was quick to respond, briefing the media that “since 2015, when he incessantly attacked Likud and the prime minister, Gideon Saar has only one objective: toppling the prime minister.”

The rivalry between Mr Netanyahu and the popular Likud politician, who served in the past as education and interior minister, is nothing new, of course.

Mr Saar’s decision in 2014 to take a break from frontline politics was widely perceived as a personal vote of no-confidence in the prime minister.

When he made his return last year, Mr Netanyahu lobbied behind the scenes against his candidacy and even claimed that Mr Saar and President Reuven Rivlin, another veteran Likudnik who has been critical of the prime minister, had a secret plan to replace him.

Despite this, Mr Saar won the fourth spot on the Likud’s candidate list in the party-wide primaries.

Now back in the Knesset, few expect Mr Saar to be made a minister; the enmity between him and Mr Netanyahu is too deep. Instead, he will serve as the internal opposition to the prime minister.

He said: “I will keep on expressing opinions on the central national issues and even fighting for them without fear. That is the purpose of the mission I have been given by Likud members.”

One Likud member, who asked to remain anonymous, commented: “Many people in the party can’t wait for Bibi to leave, especially those of us whose families have been in the movement for generations.

“Very few of us say so openly because we prefer not to confront the masses of new members who are fanatical Netanyahu-supporters. Saar is now going to be the leader of those who feel Netanyahu has taken the party to extremes and made it into one man’s private platform.”

The significance of Mr Saar’s return to to the Knesset is not only as a focal point for internal dissent.

He could also lead opposition from within the coalition to expected legislation that is to grant Mr Netanyahu immunity from prosecution in the multiple cases of corruption currently standing against him.

The coalition, yet to be formed, is expected to number 65 Knesset members. But with the Kulanu party’s four members opposing any immunity laws, all it will take is one or two Likud MKs to deny a majority in a close vote and block the legislation.

Likud is not a party given to regicide. In nearly a century since its political forerunner, the Zionist Revisionist Union, was founded, the movement has had only five leaders.

But to cause serious problems for the prime minister, Mr Saar does not need to launch a leadership bid quite yet. It will be enough for him just to withhold his vote at the key moment.