The Tanjung Piai by-election, which witnessed BN trouncing Pakatan Harapan, is a referendum on Prime Minister Dr Mahathir Mohamad's leadership, said Syed Husin Ali.
According to the former PKR deputy president, the message is loud and clear.
“The results are clear. The people are disappointed and want to teach Harapan, especially Dr M (a lesson),” he tweeted this evening when it became apparent BN was headed for a landslide win.
Syed Husin also suggested that Mahathir should step down following the electoral debacle.
“He (Mahathir) knows what should be done with immediate effect. Don't delay it any longer,” he added.
Elaborating later, Syed Husin said Mahathir should take responsibility for Harapan's massive defeat.
"A large number of the rakyat are unhappy with Mahathir's leadership which has slid to his and Umno's old ways.
"Changes that the people have hoped for seem to be so slow in coming. So the rakyat have spoken.
"It's best that Mahathir withdraws gracefully and make way to (PKR president) Anwar Ibrahim as soon as possible so that the latter can bring about reforms and prepare adequately for the coming general elections.
"Harapan should never be a one-term government," he said in a text message to Malaysiakini.
Mahathir personally campaigned for Harapan candidate Karmaine Sardini, speaking at a ceramah in the parliamentary constituency in Johor on Wednesday night.
Yesterday, the prime minister penned a letter to the voters urging them to reject BN candidate Wee Jeck Seng and cautioned them against the racial politics perpetuated by Umno and PAS.
The Harapan candidate is from Bersatu and the former MP Dr Md Farid Md Rafik, whose death led to the by-election, was also from Bersatu.
Mahathir is the founder and chairperson of Bersatu.
In September, Syed Husin excoriated Mahathir for failing to outline a clear transition of power plan and questioned if other Harapan leaders had been stymied by him.
Syed Husin also criticised Mahathir for downplaying his successor's ability to lead, calling it a betrayal and insult to Harapan.
The prime minister had, during a dialogue session in New York on Thursday, said: "I cannot guarantee that somebody who succeeds me will do well, or maybe not too well."
In an interview with Malaysiakini later, Syed Husin claimed that Mahathir had reverted to authoritarianism.
“Mahathir has become the old Mahathir, especially in the past few months. Old Mahathir means he is dictatorial or authoritarian," he said.
His criticism of the premier courted flak from Bersatu Youth chief Syed Saddiq Syed Abdul Rahman as well as Mahathir loyalist Khairuddin Abu Hassan.
Khairuddin claimed that Mahathir's designated successor, Anwar, was not qualified to helm the nation and warned that the nation could witness a repeat of the 1998 fallout between the two leaders.
Despite the repeated assurances from both Mahathir and Anwar that the succession plan would proceed as promised, speculation had been rife there it might not materialise.
Meanwhile, former de facto law minister Zaid Ibrahim said the Tanjung Piai results did not come as a surprise.
“Tanjung Piai is no surprise. Many voters still think PM is the leader of BN. That is how popular he is,” he tweeted.