Lawmakers had long enjoyed immunity preventing their arrest or prosecution without agreement from parliament -- a rule that allowed parties to make deals to delay such cases.

But on Tuesday, the supreme court revoked previous rulings requiring such parliamentary approval "in all cases against House of Representatives members, whether crimes, misdemeanours or wrongdoing".

The only exceptions would be in cases where arrest warrants are issued over "crimes with no witnesses".

In all other cases, "members of parliament have no immunity and legal measures may be taken against them directly" when they are accused of crimes.

The top court, charged with interpreting Iraq's post-2003 constitution, had previously granted parliamentarians sweeping immunity with few exceptions.

But dozens of lawmakers stand accused of graft and extortion, in cases that could now move forward.

"Courts may now rule on corruption cases" that would previously have required a green light from parliament, the court said in Tuesday's ruling.

Iraq has suffered from decades of corruption both before and after the 2003 US-led invasion that toppled dictator Saddam Hussein.

It ranks 21st from bottom in Transparency International's Corruption Perceptions Index.

Tuesday's ruling comes two days after President Barham Saleh presented a draft law to parliament to fight corruption, recover stolen funds and hold perpetrators to account.

Saleh said $150 billion from oil had been smuggled out of the country since Saddam was ousted, calling graft "pervasive practice that has plagued our great nation".

Endemic corruption was one of the drivers of protests that shook Iraq from October 2019 to June 2020.