A Zimbabwe judge has dismissed a lawsuit brought against the country's prime minister by a jilted ex-lover to stop him marrying another woman this week.

High Court Judge Antonia Guvava on Wednesday ruled that a marriage under tribal laws between Morgan Tsvangirai and an ex-lover is not valid under Zimbabwe's legal system.

The 60-year-old Tsvangirai, who is in a three-year shaky coalition with President Robert Mugabe, paid $36,000 and five cattle in traditional bride price for the woman he acknowledged had been his lover.

Tsvangirai denies formally marrying her and insists he paid damages to the family for making her pregnant. She then miscarried. His lawyers say he ditched the complainant after 12 days.

Tsvangirai plans to marry a 35-year-old daughter of a Mugabe party loyalist in Harare on Saturday.