Tun Dr Mahathir Mohamad's call for Barisan Nasional (BN) to be defeated in the Sungai Besar and Kuala Kangsar by-elections points to a plot to bring down the coalition, says UMNO secretary-general Datuk Seri Tengku Adnan Tengku Mansor.

He noted that the former prime minister had tried to pull down UMNO president and BN chairman Datuk Seri Najib Tun Razak (who is also prime minister), but now his intention was to pull down BN.

"Earlier, he was talking about pulling down the president, now he's talking about pulling down BN," he told reporters at Parliament here today.

Tengku Adnan said the party was unable to accept this.

"It's clear-cut that he's with the opposition and that he wants to kill the party," he said.

It was reported that Dr Mahathir had made the remarks at an event in Shah Alam on Saturday.

Meanwhile, the UMNO secretary-general said former deputy prime minister Tan Sri Muhyiddin Yassin and former Kedah menteri besar Datuk Seri Mukhriz Mahathir should be sacked from the party.

"My personal recommendation...to me, I would have sacked them a long time ago," he said, noting, however, that Datuk Seri Mohamed Shafie Apdal had not stood together on the opposition stage.

He said the UMNO supreme council would decide on the issue at its meeting expected to take place at the end of the month, with recommendations having been put forward by the party disciplinary committee.