People wishing to follow proceedings from parliament's Strangers' Gallery will not be allowed to carry any belongings in with them after the Graffitti group interrupted the Budget speech on Monday.

Speaker Anġlu Farrugia told the House on Tuesday said the protest was a clear breach of parliamentary privilege and he was therefore referring the matter to the House Privileges Committee.

Members of the group who were sitting in the Strangers' Gallery overlooking the Chamber interrupted Finance Minister Clyde Caruana at the opening of his address, throwing flyers at MPs while unfurling a banner and chanting 'Singing to the tune of the developers'. They were escorted out of the building by parliamentary staff.

In a ruling about the incident, the Speaker said that apart from going through metal detectors and registering their identity at the front desk, as is currently the practice, all people who wish to follow sittings from the Strangers' Gallery will henceforth also be asked to leave all their belongings, including mobile phones, in a secure place outside the chamber and collect them again on their way out.

Anyone who refuses will not be allowed in, and parliament reserved the right to close the gallery altogether.

Such measures, he said, were in line with the practice in the UK's House of Commons. 

Farrugia explained that the activists managed to sneak in because they registered as students. They did not carry any weapons or prohibited objects and security personnel therefore had no reason to stop them from entering the chamber.

He noted that the protest had defied his own warning before the budget speech began that people in the gallery were to remain silent for the duration of the speech and were not to show any signs of approval or disapproval.

He also noted that they refused to obey the orders of parliament officials when they were asked to leave the chamber, and some refused.

Officials were even lightly injured he said.