During his appearance at the Iraq war inquiry, above, Tony Blair claimed Iran now poses a similar threat to that of Saddam seven years ago. Photograph: IRAQINQUIRY.ORG/EPA

Tony Blair has been accused of warmongering spin for claiming that western powers might be forced to invade Iran because it poses as serious a threat as Saddam Hussein.

Sir Richard Dalton, a former British ambassador to Iran, accused Blair of trying to make confrontation with Iran an electoral issue after the former prime minister repeatedly singled out its Islamic regime as a global threat in his evidence to the Iraq war inquiry yesterday.

Blair said many of the arguments that led him to confront the “profoundly wicked, almost psychopathic” Saddam Hussein seven years ago now applied to the regime in Tehran.

“We face the same problem about Iran today,” he told the Chilcot inquiry.

Dalton, the UK ambassador to Iran from 2002 until 2006, said it was essential that all the political parties made clear in the run-up to the general election that there would be no repeat of Blair’s actions in respect of Iran.

“One result of Tony Blair’s intervention on Iran – he mentioned Iran 58 times – is to put the question of confronting Iran into play in the election,” he told the BBC Radio 4 Today programme.

“We need to be much clearer, as voters, with our politicians and with our candidates that we expect a different behaviour and a greater integrity in our democracy next time.”

Blair warned that the international community must be prepared to take a “very hard, tough line” with Iran, a country “linked up with terrorist groups”, to prevent it from developing nuclear weapons.

He said that if action had not been taken in 2003 to topple Saddam, Iraq could be locked in a nuclear arms race with Iran with potentially devastating consequences for the region and the wider world.

The former prime minister attacked the Islamic regime for fomenting the insurgency that followed the invasion of Iraq by US and UK forces.

He claimed that Iran, which follows Shia Islam, had supported al-Qaida, despite it following the rival Sunni branch of the faith, because they both had a common interest in destabilising Iraq.

Dalton dismissed as a “piece of spin” Blair’s claim that the Iranians almost caused the failure of the coalition mission in Iraq through their support for the insurgency.

“To say that Iran was the principal reason seemed to me to be part of a broader argument which he was trying to make, namely that it makes what he did in Iraq look better if he extends it to the future and says the policies then might have to be applied. But Iran is a completely different situation,” Dalton said.