The eyewitnesses were a delegation from the Maltese Parliament’s foreign affairs committee who sat just one row behind the two men who hurled the powder at Mr Blair during the Prime Minister’s

question time yesterday. Jason Azzopardi said: “We were seated in the strangers’ gallery at about 12.15pm when a dark-skinned man, possibly Arab or Asian, stood up and threw two fistfulls of flour at Mr Blair.”

“Another man stood up and opened up a placard and the two began shouting in an unfamiliar language, but we definetely heard the words ‘Middle East’,” said Dr Azzopardi.

He continued: “The flour hit Mr Blair straight in his back and before we knew it, four House of Commons marshals tried to restrain the men. There was a commotion, but they had them under control very soon.”

Dr Azzopardi said that an immediate full-scale alert was sounded. “They had a lock-down and no one was allowed in or out of the building. Mr Blair was whisked away to safety and tests on the substance began immediately,” he said.

Dr Azzopardi said that they were eventually allowed out of the building at about 1.05pm. “The place was full of police officers, decontamination officials and there were numerous ambulances outside,” he said.

Dr Azzopardi said he could not understand how the men had got in because the Maltese delegation had been submitted to at least three frisk searches before entering the House of Commons.

Sky News later carried a report to announce that the powder was nothing more than coloured cornflour. Dr Azzopardi was accompanied by Opposition Foreign Affairs spokesman Leo Brincat.