CONSERVATIVE Party chief whip David Maclean has said he may have made a mistake by ordering out Tory MPs from the Commons chamber after purple flour was thrown at the Prime Minister.

However, the MP for Penrith and the Border said a security plan, instructing members to remain in the House in the wake of such an attack, had not been communicated to him.

He said he welcomed the "stupid, stupid stunt" because it was a wake-up call that gave the House of Commons one last chance to sort out its security.

Mr Maclean was in the Commons during Prime Minister's questions last Wednesday when flour was thrown at Tony Blair.

"I heard the ruckus, I saw what I thought was smoke coming down it turned out to be dust.

"The Speaker immediately said "sitting suspended" and left the chamber. People were standing up and milling about and I took command of my own side and said "move, move, get out"."

Mr Maclean said the reaction was the correct one for a gas attack, but would have been incorrect in a biological attack, during which it is important not to spread the contamination.

After the incident, security staff and police told the Chief Whip that the plan in such an event was for MPs to remain in their seats.

Asked for his reaction to the fact that he had not been told of this plan he said: "Shall we say I'm having strong words with some people.

"That's going to be subject of an inquiry. If there's a plan we have got to indicate it to everybody. It was an eye-opener, it was a good dry run, and our last chance to get it right.

"It could have been very, very serious. An awful lot of things went wrong and it tested the system."

The key to the inquiry findings would be stepping up security without keeping people out, said Mr Maclean l Two men have been charged in connection with the incident.