London, May 20 (Reuters): The British government scrambled today to tighten security in parliament after protesters hurled a condom filled with purple powder, striking Prime Minister Tony Blair.

The incident sparked fears that lax security could have let terrorists launch a chemical or biological attack on the heart of UK government. Two activists from a fathers’ rights group threw what turned out to be harmless dyed flour at Blair during his House of Commons question time yesterday, when nearly all the top cabinet members were huddled around him.

The government’s leader in parliament, Peter Hain, met officials of Britain’s MI5 domestic security agency today to discuss new measures. He said the House of Commons would be allowed to debate their recommendations next week. A wider security service review was already looking into ways to improve safeguards in the riverside building, which is partly surrounded by concrete blocks to prevent car bomb attacks.

That inquiry will report in the summer.

“Some hard lessons need to be learned about what happened yesterday and there will be... recommendations coming from the security service which we will be able to consider early next week,” Hain told parliament.

Police said the two men remained in custody. Fellow activists protested outside the London police station in which they were held.