“It has given Malaysia a bad name as Najib is being accused of stealing,” he said when cross-examined by lawyer Jahaberdeen Mohamed Yunoos.
He said Umno, the dominant party in the government, was no longer the party of yesteryear.
“The present Umno is now Parti Najib,” said the former prime minister who was in the witness stand for about 15 minutes.
Dr Mahathir told the packed courtroom that he had been attempting to overthrow Najib from power since 2014.
He was testifying in his son Mukhriz’s defamation suit against Tengku Sariffuddin Ahmad, the prime minister’s press secretary.
On May 3 last year, Mukhriz filed the suit over four media statements issued by Tengku Sariffuddin on April 15, 20, 23 and 26.
Mukhriz’s complaint was that Tengku Sariffuddin’s alleged defamatory statements gave the impression that Mahathir was grooming him to become prime minister.
In his defence, Tengku Sariffuddin said he had never defamed Mukhriz in any of his media statements, seeking only to clarify issues and untruths spread about Najib.
Tengku Sariffuddin said the statements were published based on qualified privilege and without malice.
He said his media statements were made in his official capacity to prevent rumours or political allegations against the prime minister.
Earlier, Dr Mahathir said he was Umno vice-president when the then prime minister Hussein Onn appointed him as deputy prime minister in 1976.
“When Anwar Ibrahim was sacked, I (as prime minister) appointed party vice-president Abdullah Ahmad Badawi as my deputy in the government, ” he told the court.
Mahathir said it was the discretion of the prime minister, who was also Umno president, to appoint, a senior party leader to be his deputy in the government.
Lawyer Mohamed Haniff Khatri Abdulla informed Justice Ahmad Zaidi Ibrahim that Mukhriz was closing his case with two witnesses.
Hearing was adjourned to Sept 21 with Tengku Sariffuddin to give evidence.