Biti, a veteran figure in the Movement for Democratic Change (MDC), fled to Zambia yesterday claiming asylum, reportedly facing charges at home of inciting post-election violence.
Zambian authorities swiftly refused him asylum, but Phiri said Biti's legal team had managed to challenge the decision, keeping Biti in Zambia.
But authorities have ignored the ruling and deported him, Phiri said.
"He is on the Zimbabwe side," he confirmed. "This is really embarrassing."
A hearing at Zambia's High Court, where Biti was supposed to appear, will go ahead today in his absence, Phiri added.
Biti, an internationally-respected finance minister in Zimbabwe's troubled 2009-2013 power-sharing government, had proclaimed a victory for the opposition before the results came in.
According to Zimbabwe's state-run Chronicle newspaper, he is among nine suspects sought for inciting protests over alleged rigging which turned deadly.
The army opened fire with live ammunition on the opposition protesters, killing six people and prompting an international outcry.
The election has been marred by accusations of a crackdown on opponents, with arrests and beatings, as well as the deadly violence and rigging claims.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)