A U.K. parliamentary report says the risk of permanent psychological side effects on mefloquine is “unacceptable” for British soldiers.

A controversial drug that has been given to thousands of Canadian soldiers and is still in use in the military was deemed too risky for British troops in a landmark report released Tuesday.

The report by MPs on the U.K. parliamentary defence committee recommended that the British military use the anti-malaria drug mefloquine only as a “drug of last resort,” due to the risk of severe psychological side effects.

While adverse reactions to the drug are “in the minority, we do not believe that the risk and severity of these side effects are acceptable for our military personnel overseas,” the report said.

In Canada, the report was welcomed by veterans who say the Canadian military has lagged behind its allies in restricting the drug’s use and addressing the legacy of long-term side effects among soldiers.

“Canada should get in lockstep with its allies on this issue” said former Canadian Airborne Regiment soldier John Dowe, head of a three-country advocacy group pushing for an end to the military use of mefloquine.