It's very important to him that there is proof of the weapons, because getting rid of them was the reason he gave for getting involved in the war.
In a TV interview the Prime Minister said the government does have information about the weapons, and will publish it when it's all ready.
But not everyone agrees with Tony Blair, including former cabinet minister Clare Short, who resigned from the government in May.
She believes that the government deliberately made things sound more dangerous than they were to justify going to war.
She does think that Iraq was trying to build the weapons, but doesn't think they were as much of threat as the government said they were.