Dr Mahathir Mohamad has denied forgetting his actions as prime minister and Umno president when the ruling party was deregistered by the Registrar of Societies (ROS) in 1988.

Instead, he said Deputy Home Minister Nur Jazlan Mohamed, who accused him of forgetting history, doesn't know how to make proper comparisons.

"I have not forgotten. It is Nur Jazlan who doesn't understand by making comparisons between apples and oranges, and believing apples and oranges are the same," he wrote in a blog post last night.

Mahathir said during his time, the ROS had acted independently and moved against Umno despite it being part of the government.

"Now the ROS only disturbs opposition parties. Could ROS declare Umno illegal? There is a case to do so (now).

"If ROS declares Umno illegal, then it will be the same as what happened in my time," he said.

Mahathir was referring to Umno's move to further postpone its party elections to next year, a move that former party members say is against its constitution.

The Bersatu chairperson was responding to Nur Jazlan's remarks on Monday that Mahathir had forgotten his past in criticising the ROS.

“He seems to have forgotten what he did 30 years ago as ROS is now executing its duty fairly and taking the interests of Bersatu members into account," the deputy minister was quoted as saying by The Star.

Nur Jazlan also claimed that when Umno was deregistered, Mahathir had tried to compel the ROS to side with the party.

In an immediate response, Nur Jazlan today said Mahathir had amended Umno's constitution in order to prevent further legal challenges. 

"The purpose (of doing so) was to strengthen his position as Umno president and PM. By the way, he used the same provision to sack Anwar (Ibrahim) and supporters," wrote Nur Jazlan on Twitter.