A former U.N envoy to Afghanistan on has questioned the “mental stability” of Hamid Karzai and suggested the Afghan president may be using drugs.

In an interview on MSNBC’s “The Daily Rundown,” Peter Galbraith described Karzai as “off-balance” and “emotional.” Galbraith also called for President Barack Obama to vastly limit Karzai’s power to appoint officials within the war-torn country until he proves himself a reliable partner to the U.S.

“He’s prone to tirades. He can be very emotional, act impulsively. In fact, some of the palace insiders say that he has a certain fondness for some of Afghanistan’s most profitable exports,” said Galbraith, in an apparent reference to opium or heroin.

When asked whether he meant Karzai has a substance abuse problem , Galbraith responded: “There are reports to that effect. But whatever the cause is, the reality is that he is — he can be very emotional…”

Galbraith was fired by the United Nations in September as the U.N.’s No. 2 official in Afghanistan after he openly accused his boss, Kai Eide, of concealing election fraud that benefited the campaign of the incumbent president. Eide angrily denied the accusation.