A government minister launched a rare attack Monday on Iran's downplaying of the impact of international sanctions, saying that "lying" to the public over the measures had left the country "backward".

Mohammad Reza Nematzadeh, the industry, mining and trade minister, delivered the broadside at a conference in Tehran, claiming years of statements about sanctions not hurting the country were false.

"Why should we abandon logic and swear instead or have empty gestures?" Nematzadeh asked. "Do you think the world doesn't get it that our gestures are empty? That our remarks are empty?"

The comments alluded to former president Mahmoud Ahmadinejad, whose tenure was dominated by tension over Iran's disputed nuclear programme and the sweeping economic sanctions that followed.

After long denying sanctions had harmed Iran's economy, Ahmadinejad admitted in 2012 that they had indeed caused damage.

"Using bad language and swearing is not strength," Nematzadeh said, to loud applause, in a barely veiled barb at Ahmadinejad, who was regularly criticised in Iran for using vulgar words in his speeches.

Iranian politicians are known for taking a combative stance on issues such as sanctions -- many lawmakers continue to downplay their effect -- but the strength of Nematzadeh's remarks in a public forum was rare.

"Why should we say war has no effect or sanctions have no effect?" Nematzadeh said. "Our educated youths can tell if you're lying. Why should we teach young people to lie?

"I told a person 'what if your hands and legs are tied up? Would it have no effect on you moving?'"

He praised current President Hassan Rouhani for taking a different approach to Ahmadinejad.

"We've been subjected to injustice. Mr Rouhani referred to 'unjust sanctions'. I heard this first from him," he added

Nematzadeh, now in his fourth government having also served under Ahmadinejad, cited economic progress made by former presidents Akbar Hashemi Rafsanjani and Mohammad Khatami, arguing that people ought to be better off because of their policies.

"If we consider sanctions as a blessing, then we should be constantly asking for more sanctions, which in fact happened... we kept saying: 'sanctions have no effect'.

"Let's put some cotton in their ears, scotch tape on their mouth. Why do you lie? It does have an effect. The country has become backward. There's inflation, recession. Why should young people be unemployed?" he said.

Since Rouhani took office in August 2013 the inflation rate has halved to less than 20 percent and the government has stressed it is open to foreign investment should sanctions be lifted under a nuclear deal currently being negotiated by Iran and world powers.