Commons Speaker John Bercow has ordered an "entirely independent" investigation into how a protester was able to throw a plate of shaving foam at Rupert Murdoch in Parliament.
Jonathan May-Bowles was charged with a public order offence after the incident at yesterday's much-anticipated Culture, Media and Sport Committee hearing.
The protester, who goes by the name Jonnie Marbles, threw a paper plate with white foam at the 80-year-old media mogul's face.
In a short statement to MPs, Mr Bercow said: "It is wholly unacceptable for a member of the public to treat, and to be able to treat, a witness in this way.
"It is all the more regrettable that such an incident should happen at a time when, particularly over the last few days, the work of this House and its committees has enhanced the reputation of Parliament.
"I have immediately set in hand an expert investigation into what took place, the reasons for the security failure and the lessons to be learned.
"This investigation will be entirely independent of the House authorities."
May-Bowles, 26, of Edinburgh Gardens, Windsor, was bailed to appear before City of Westminster Magistrates Court next Friday, July 29.
He is charged with behaviour causing harassment, alarm or distress in a public place under Section 5 of the Public Order Act, Scotland Yard said.
John Whittingdale, who chairs the Culture, Media and Sport Committee, welcomed the inquiry announced by Mr Bercow.
Speaking during today's debate on public confidence in the media and police, he said: "I did think it was very important that Rupert and James Murdoch and Rebekah Brooks came to Parliament.
"I was particularly sad their appearance was marred by the incident which the Speaker has referred to.
"It seemed to me not to serve the interests of those who dislike Rupert and James Murdoch. It distracted attention from the very important matters we were attempting to probe them on and it did no credit to Parliament or the committee that they were treated in that way.
"I believe the inquiry is extremely important."