"I am not going to stand by while Zanu-PF continues to violate the law, persecutes our members of parliament, spreads the language of hate, invades our productive farms, ignores our international treaties," he said.
"We want partners that are sincere. We want partners who are going to commit themselves to good governance principles. We cannot have partners of looters."
Tsvangirai joined Mugabe in a unity government in February in a bid to end political unrest that erupted after last year's disputed elections and things have improved in the past few months.
Al Jazeera's Haru Mutasa, reporting from the capital, Harare, said "compared to December last year, when things were really bad in the country ... there's now food in the shops - it's expensive, but at least people can afford it"....