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Steven Abberley threw marbles during a busy prime minister’s questions debate last October (Parliament TV)

A protester has been spared jail after he admitted throwing marbles at MPs during prime minister's questions in the House of Commons.

Steven Abberly, 28, caused a security alert during last year's debate after throwing marbles at a glass security screen while David Cameron was talking.

Westminster Magistrates' Court said the incident caused a loud bang to be heard inside the Commons, but no one was injured during the PMQ session on 22 October 2014.

Abberley was also found to have sworn at the politicians and called them "liars" before he was escorted out of the chamber.

Abberley also admitted to scrawling graffiti on the wall on the Palace of Westminster which reading "the enemy within".

He said he committed the offences because he felt like his life was "wasting away".

Prosecutor Mavis Ramkissoon told the court: "Abberley stood up and said, 'I'm sorry about this, ladies and gentlemen. You f*****g w*****s, you're just liars'.

"He produced a cloth bag and threw the contents, glass marbles, at the security screen. It caused shock and distress to members of the public present."

Shouting from the dock, Abberley rejected the prosecutors description of the event, insisting he actually called the MPs "dishonourable b******s".

When given the opportunity to speak further, Abberley explained he threw the marbles because he was seeking employment and suffering from mental illness.

"I feel like my life is wasting away where I'm living. There's nothing happening for me," he added.

Abberley, from Sutton in Surrey, pleaded guilty to using threatening words and behaviour and causing criminal damage. He was sentenced to 12 weeks for the marble throwing incident and four weeks for the graffiti. Both sentences were suspended.

Judge Quentin Purdy said: "Anyone who chooses to disrupt [proceedings] causes those attending anxiety and distress. It causes people to feel they cannot go to that place.

"That's not the way it should be."