VALLETTA, Malta—Maltese Prime Minister Lawrence Gonzi has lost his one-seat majority in Parliament, paving the way for new elections.

Monday night's crucial vote on the 2013 budget saw one lawmaker from the government's Nationalist party vote against the budget bill because he was unhappy over reforms championed by the transport minister.

No date was immediately set for elections, which had been due by the end of March in the tiny eurozone nation. Parliament is expected to be dissolved on Tuesday.