Tehran should appoint a supreme leader who will both challenge US propaganda that Iran is a war-mongering nation and reduce domestic polarisation, the country’s diminished alliance of reformist groups has said.

The Reform Front, which helped Masoud Pezeshkian become president 18 months ago, suggested that attacks on non-military US assets in the region were diminishing global support for Iran as a victim of a blatant aggression, according to comments cited in a report by the Iranian newspaper Donya-e-Eqtesad.

“The election of a new leadership of the regime could convey a message of peace and friendship with the world, and thus strengthen anti-war protests on the global stage,” the Reform Front said, according to the report. “[It] should also convey the message of the beginning of a new era in Iran; an era that promises the participation of all political and civil tastes and tendencies in the governance of the country.”

An attempt by the regime to rely on only part of society to win the war would be a “very big and unforgivable mistake”, it added. The group did not identify its favoured candidate or name anyone it believes would hinder national unity. The choice of leader is made by the 88-strong assembly of experts. Currently the government is run by a temporary tripartite council.

Widespread reports suggest Donald Trump opposes the idea of Ali Khamenei’s son Mojtaba Khamenei succeeding him as supreme leader.

Releasing political prisoners and civil activists in a general amnesty was a necessity, the reformists said. They said in a war against an enemy possessing “the most advanced military and information technologies”, society could only remain resilient if there was national unity and cohesion.

Although reformists are a weakened force inside Iran, the criticism, expressed in the context of defending the homeland, is one of the few signs of an internal debate about how the country can end its international isolation, and whether the attacks on Gulf states will prove counterproductive.

There had been reports of a widespread release of prominent political prisoners, but later it was suggested the only prisoner who had been released was Ali Shakouri-Rad, a senior reformist politician. He was arrested last month a few days after a private meeting was leaked in which he accused security bodies of deliberately escalating and even staging violence including alleged killings among their own ranks to legitimise January’s sweeping crackdown on protests. He is suffering medical issues.

The Reform Front statement said there were “legitimate national figures who are trusted and respected by civil society and international forums, who, within the framework of public diplomacy, can communicate with international circles and encourage them to be more active in the global condemnation of this aggression”.

Arguing Iran needed to attract regional and global support and cooperation, it wrote: “The expansion of attacks against US military bases and their extension to political centres affiliated with this government in the countries of the region and the failure to distinguish between the two will remove Iran from the position of being oppressed and a victim of aggression, causing an inevitable reaction from the governments of the region and their joining the global consensus against Iran, and as a result, reducing our diplomatic capacity to end the war.”

The statement added: “After the war, Iran will no longer be the Iran of the past.”

It also called on “all components in Iranian society – whether Turks, Kurds, Lors, Arabs, Baluchis, Turkmens, Persians, etc to defend Iran’s national identity, independence, and territorial integrity by relying on Iranian wisdom and understanding, recognising ethnic and cultural diversity, and respecting each other’s beliefs”.

The reformists add that opportunities were lost when recommendations from the pre-eminent reformist leader Seyyed Mohammad Khatami and the Reform Front itself last summer were not heeded.

While utterly condemning the US-Israel aggression, the group also said Iran would be in a stronger position diplomatically and in terms of social cohesion if calls for the release of political prisoners had been heeded last summer after the 12-day war.

In its statement the Reform Front – whose leadership was the subject of recent mass arrests by the security services – said “there should be no doubt that Israel’s goal in this blatant aggression is to destroy all of the country’s defence capabilities and infrastructure, overthrow the regime, and then lead to chaos, civil war, and the disintegration of the country”.

Pezeshkian’s son Yousef said the government needed to decide what it wanted its ideal post-war scenario to be since that would determine “the decisions taken, the operations we carry out and the words we say”.

He openly discussed the factors at play that would determine the outcome of the war, saying the key assessment was whether Iran’s “endurance [will] be greater than [that of] the enemy”. This will rest in part on the issue of weapons stockpiles.

In the main, state-aligned Iranian TV and websites are focusing on the stated military successes of the security forces, or on civilian deaths, with little being broadcast about the damage being inflicted on Iranian missile launchers and security apparatus.