Andrew Murray, with Mr Corbyn in 2009, has been accessing parliament as a visitor

Jeremy Corbyn is under investigation for a possible breach of parliament’s strict security rules after two of his most senior aides spent months working in the Commons without being vetted.

Officials began their second investigation into the Labour leader in a week after it emerged that Andrew Murray, a political adviser, and Iram Awan, Mr Corbyn’s private secretary, had been accessing parliament as visitors.

Mr Murray, 60, a former communist who also works for the trade union Unite, has been one of Mr Corbyn’s most important ideological advisers since February, and works between one and two days a week for the Labour leader. He was a founding chairman of the Stop the War campaign and was succeeded in that role by Mr Corbyn.

Iram Awan, with her partner Ian Chamberlain, who is linked to Stop the War

Ms Awan,