JOHANNESBURG — South Africa’s highest court ruled on Friday that Parliament had failed to hold President Jacob Zuma accountable in a long-running corruption case, putting pressure on the weakened leader to resign as his party tries to reinvent itself.

The Constitutional Court ruled that Parliament — which is dominated by Mr. Zuma’s African National Congress and has stood behind the scandal-plagued president during his eight years in office — had failed to properly investigate Mr. Zuma’s conduct when it voted last year not to impeach him.

“The assembly did not hold the president to account as was required” by a section of the Constitution that deals with the president’s removal, Judge Chris Jafta said in handing down the court’s judgment.

The court ordered lawmakers to create rules to regulate a president’s impeachment, a move that makes it more likely that A.N.C. leaders will try to force Mr. Zuma’s removal as president, to avoid the distraction and embarrassment of potentially impeaching a lame-duck leader.