Zimbabwe's army is suffering food shortages after recruiting thousands of new soldiers without authority from the cash-strapped treasury, Finance Minister Tendai Biti said on Thursday.

Zimbabwe, struggling to recover from a decade-long economic decline that critics blame on long-serving President Robert Mugabe's ZANU-PF party, is spending a large share of its $4 billion budget for 2012 on wages.

Biti told parliament that the monthly state wage bill had risen to $190 million following what he called illegal hiring of 4,600 recruits by the army and 5,400 people by the Interior Ministry and other government departments from January to May.

Both the defence and interior ministries are run by ZANU-PF ministers, while Biti is a member of the MDC party that joined ZANU-PF in an uneasy power-sharing government after disputed elections in 2008.

Biti said the "illegal recruitment exercise" had created "serious problems, especially in military barracks, where food shortages have been recorded", and that the government had had to divert money meant for pensions to cover the new recruits.

There was no immediate comment from the army or the public service commission responsible for state workers.

Elections are expected in Zimbabwe within a year, and there are major question marks over the military's neutrality.

Defence chiefs have publicly backed Mugabe's candidature ahead of previous elections and have vowed never to salute a leader who did not take part in the 1970s independence war, a reference to the MDC leader, Prime Minister Morgan Tsvangirai.

A year ago, state media reported a top general as saying military involvement in politics was justified because Tsvangirai was a security threat fronting Western interests.