MI5 opened a file on Jeremy Corbyn amid concerns over his links to the IRA, The Telegraph has discovered.

The Labour leader was investigated over fears that he could have been a threat to national security at a time when he was supporting convicted terrorists and campaigning for a unified Ireland.

The revelations come as a Telegraph investigation reveals Mr Corbyn’s full links to the IRA, including his support for one of the Balcombe Street gang who waged a 14-month bombing campaign across south-east England, and his links to the bomb maker believed to have been behind the Hyde Park and Regent's Park devices.

Mr Corbyn also shared a platform with a wanted IRA killer and John McDonnell, his shadow Chancellor, claimed that the pair of them used to “pin people against the wall” in the House of Commons to lobby them on behalf of Ireland.