"We must no longer trust those who pretend to be in the inclusive government and have jumped in and out of it," Mugabe was quoted as saying in the state-run Herald newspaper.
"They can never be true and genuine partners and they have proved to be dishonest.
"We, however, want to assure you that we will not allow the situation to continue like that."
Tsvangirai, the former opposition leader, joined the unity government with his longtime rival Mugabe in February in a bid to end political violence and halt the nation's economic freefall.
But two weeks ago he suspended co-operation with Mugabe's party in protest over the arrest of Roy Bennett, his nominee for deputy agriculture minister.
A team from the Southern African Development Community (SADC) arrived in Harare on Wednesday in hopes of breaking the deadlock.
On Friday, the delegation announced that there was need for a full SADC summit to address problems related to the power-sharing agreement.
Mugabe said the decision by Tsvangirai's party to halt co-operation with the 85-year-old president's ZANU-PF was hypocritical.
"ZANU-PF is not government, but in government. It is part of government like the other two parties.
"Cabinet is not a party affair. That kind of hypocrisy should be seen as it is.
"What kind of sincerity is that? We go into government, form policies, hold investment conferences, (but) we have a part of the government striking against themselves."
He said the government would continue to work despite the move by Tsvangirai's party.
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Murrow