The Home Office is investigating whether Iran is funding Palestine Action, while the Government moves to designate it a terrorist organisation.
Officials are understood to be probing the group's source of donations amid concerns it is not bound by financial transparency rules.
There are fears Iran could be providing money, via proxies, given their objectives of 'dismantling the apartheid regime in Israel' are aligned.
Home Secretary Yvette Cooper is due to update MPs next week on the proposals to make it a criminal offence to belong to or support Palestine Action.
The move comes after the group posted footage online showing two people inside the base at RAF Brize Norton in Oxfordshire.
