The previous Conservative government did not proscribe the IRGC, despite suggesting it would do so in 2023.
Maintaining diplomatic relations with Iran has been cited as a reason for not proscribing the IRGC in the past.
Conservative shadow foreign secretary Priti Patel said: “Labour promised action on IRGC proscription but, despite reviews and rising threats, they have failed to deliver.
“Our allies from Europe to Canada and the Gulf have already acted, and the UK is lagging behind.”
Labour had promised to proscribe the IRGC as a terrorist organisation before the general election in 2024.
But once in power, the Labour government stepped back from doing so while ministers reviewed options for dealing with state-linked organisations.
The government already has powers to proscribe organisations under the Terrorism Act 2000.
Other groups like the Iran-backed Hezbollah have been banned under that law.
But last year, the government’s independent reviewer of terror legislation, Jonathan Hall KC, said new powers were needed to tackle state-sponsored organisations.
In a report, external, Hall recommended a law change that would give the government powers “equivalent to proscription under the Terrorism Act 2000”.
“By way of example, this strong power would be available for use against the Islamic Revolutionary Guard Corps,” Hall said.
Yvette Cooper, when she was home secretary last year, said the government had accepted Hall’s recommendations.
In May last year, Cooper said, external the government would “draw up new powers modelled on counter terrorism powers in a series of areas to tackle these state threats”.
She added: “And crucially I can tell the House we will create a new power of proscription to cover state threats – a power that is stronger than current national security act powers in allowing us to restrict the activity and operations of foreign state backed organisations in the UK.”