Dr David Clark, the shadow defence secretary, said last night that private information supplied to him showed that the Government's official inquiry published last December had "grossly minimised" the contamination of troops.
The information, seen by the Independent on Sunday, indicates that soldiers' tents, at a camp used by most Britons who fought in the Gulf, were repeatedly sprayed with a rain of dangerous organophosphates (OPs), even when they were occupied.
The Ministry of Defence's official Organophosphate Pesticide Investigation Team inquiry, to which it still adheres, only admits to one spraying of the camp, Baldrick Lines, at Al Jubail, Saudi Arabia, and insists that this happened when it was empty.
The report said it had found "no evidence" that spraying "has been conducted improperly".
Last week the Armed Forces Minister Nicholas Soames refused to resign after admitting misleading Parliament over the use of OP pesticides in the Gulf.
The new evidence on spraying, supplied by one of the men who carried it out, who insists on anonymity for fear of reprisals by the ministry, says: "All of the troops passing through this camp were exposed to organophosphorous insecticides, either while they were being sprayed or when they were evaporating from the canvas in the high temperatures."
Dr Clark said last night: "This scandal never seems to end. Every bit of information has had to be dragged reluctantly out of the Government."
The Ministry of Defence said that its inquiry's report was "definitive".