The MPs were arrested on Wednesday and charged with disorderly conduct, their lawyer Tafadzwa Mugabe said.
Co-operation between the Movement for Democratic Change and Robert Mugabe’s Zanu PF is crucial as the government tries to win vital funding from foreign donors who are demanding faster political and economic reforms.
The MDC lawmakers were held at a police station for several hours after they went to the Finance Ministry offices to enquire about MPs’ allowances and a vehicle loan scheme.
"They’ve been released and told they should come back on Thursday. They have been charged with disorderly conduct and behaving in an insulting, threatening and abusive manner and for a public breach of the peace," the lawyer said.
"They had gone to the permanent secretary’s office to enquire about allowances and the vehicle scheme, but were told he was not there. They offered to wait and when he did not turn up, somebody made a report to the police."
Robert Mugabe’s opponents and the small remaining community of white farmers still complain of detentions and harassment, but the unity government has functioned better than many believed possible.
Tsvangirai’s party, which defeated Zanu PF in last year’s parliamentary polls, accuses Mugabe of plotting to whittle away its majority by arresting its lawmakers on various charges.
Before Wednesday’s arrests, at least seven MDC MPs faced charges that the party described as trumped up, and five have already been convicted of various crimes.
Four of them were sentenced to more than six months in jail, which automatically disqualifies them from holding their parliamentary seats, according to Zimbabwean law.
Analysts believe the coalition has little choice but to hold together because catastrophe would follow if it fell apart.