It is believed that an alleged break-in at the Houses of Parliament last night centred on the suite of offices used by Labour leader Ed Miliband.
Scotland Yard refused to confirm the reports, but it is understood that a member of Mr Miliband's staff found that a door had been forced in the Norman Shaw buildings.
The incident is not thought to have involved the specific room that Mr Miliband uses as his personal office.
It is not clear whether anything had been taken.
More top news
The mother of a former altar boy who tried to blow up a train insisted he was 'a big softie' who didn't want to hurt anyone.
Its current five year licence comes to an end next Tuesday.
Extra armed police will guard major sporting events in London this weekend after the military was drafted in to protect key locations.