Destitute Zimbabwe plans to borrow from local companies to raise US$100 million (NZ$117m) needed to hold a referendum on a new constitution, Prime Minister Morgan Tsvangirai says.

The southern African country will vote in March on whether to adopt a new charter approved by parliament that seeks to curb sweeping presidential powers while strengthening state institutions such as the cabinet, parliament and judiciary.

Rivals Tsvangirai and veteran President Robert Mugabe formed a power-sharing government after a disputed 2008 election and agreed to hold fresh polls only after adopting a new constitution.

Tsvangirai and one of his deputies in government, Arthur Mutambara, said the government wanted to borrow from firms, including mines and banks, as well as issuing Treasury bills.

"We have put in place a mechanism to raise funds for the referendum," Tsvangirai told reporters at a press conference.

Mutambara added: "We are saying to the private sector: 'This is your country, political stability is in your best interest,."

Harare has a history of defaulting on its debt and has seen its external debt rise to more than $10 billion.

Zimbabwe's economy shrunk by as much as 40 per cent between 2000 and 2008 - according to official figures - a decline blamed on Mugabe's policies such as the seizure of white-owned farms.

Most foreign donors have withheld money, pressing for political and economic reforms.

Finance Minister Tendai Biti has already approached the United Nations to help raise money for general elections, which by law are due when the current presidential and parliamentary terms expire at the end of June.

Tsvangirai said the United Nations had a team in the country to discuss the request.

- Reuters