Britain's opposition Labour Party chief Ed Miliband's parliamentary office has been reportedly burgled.
Though it's still unclear whether anything was stolen from Miliband's office at House of Commons on Friday evening, British intelligence agency MI5 has launched a major probe into the "sensitive" incident, the 'Sunday Express' reported.
The 42-year-old is the most senior politician outside the UK government to receive regular updates from MI5 and external spy agency MI6. He is also regularly briefed by Downing Street on all matters relating to security.
"While the police have not confirmed what, if anything, was taken, Mr Miliband is party to information of the utmost importance and sensitivity.
"For someone to break into his office suite, start going through drawers and flicking through folders full of official documents is extremely worrying. This will not be taken lightly," a senior MI5 source was quoted as saying.
In fact, the incident came to light late on Friday evening when Miliband was not in his parliamentary office.
Police were called just before 7 PM to reports of forced entry to premises in Norman Shaw South building, the former Scotland Yard headquarters, next to Portcullis House.
Although Miliband's personal office, in which he has a private safe containing top secret documents, was untouched, an aide reported damage to the front door of his private suite used by the Labour leader to brief staff.
MI5 officials later conducted a thorough sweep to see if any highly sensitive policy papers had been taken. They also checked to see if any listening devices had been planted.
A Labour spokesman said: "It looks like the policy office has been deliberately targeted. We don't know if anything has been taken or the motivation for this crime but we are deeply concerned that it can take place in Palace of Westminster."
Last year, there were 40 incidents of theft at the House of Commons, including 25 laptops and three mobiles.