Malaysia's highest court has allowed opposition leader Anwar Ibrahim to challenge his 1998 dismissal as a deputy prime minister, a surprise decision that his lawyer described Tuesday as "very significant."

The Federal Court's three judges decided unanimously Monday that Anwar would be allowed to appeal earlier court verdicts dismissing his contention that then-Prime Minister Mahathir Mohamad fired him unlawfully, according to his lawyer, Karpal Singh.

Anwar, who now leads a strong opposition coalition, was fired in 1998 after falling out with Mahathir. Instead of becoming the next prime minister, as was widely expected at the time, he ended up in prison, convicted on sodomy and corruption charges he said were trumped up.

Anwar asked the courts to reinstate him, claiming Mahathir had acted unconstitutionally by dismissing him without the approval of the king, the country's titular ruler. But a high court and subsequently an appeal court dismissed his case.