Lim Kit Siang has dismissed Najib Abdul Razak's invitation for him to join Umno as nothing more than a joke.

Without mincing words, the DAP veteran said "only a kleptocrat who is insane" would want to join Umno at this juncture when it had "not cleansed itself of global kleptocracy".

"For this reason, I am not so lacking in integrity and sanity as to take up Najib’s offer," he added in a statement this afternoon.

Yesterday, Najib had offered Lim to join Umno and even filled up his name as the proposer in the online membership form.

The former prime minister also quipped that Lim's application to become a member could be rejected on the grounds of lacking integrity and sanity.

Najib's remarks came after Lim had linked Ahmad Zahid Hamidi's return to helm Umno, after a protracted leave of absence, to Najib.

Meanwhile, the DAP veteran, in his media statement, asked Najib if Umno had cleansed itself of global kleptocracy with Zahid at the helm.

“How can this be the case when Zahid is facing 87 charges related to corruption, money-laundering, bribery and criminal breach of trust, 45 charges more than what Najib himself is facing, with Zahid creating a new national record as a Malaysian facing the most number of corruption charges in our courts,” he added.

Lim also asked if the party's number two, Mohamad Hasan, in his capacity as acting Umno president, had cleansed the party of global kleptocracy during Zahid's garden leave.

“Why did Zahid go on garden leave as Umno president for the last six months?

“Have the reasons why Zahid had gone on garden leave been resolved in the past six months, and if not, why had Zahid returned unilaterally and without consultation of the Umno supreme council from garden leave?” he added.

The DAP leader also questioned if Umno's membership is open to all Malaysians or only to kleptocrats?

On the same note, Lim said he would not invite Najib to join DAP.

"Najib should know that I would not invite him to join DAP, for any such invitation will raise questions about the integrity and sanity of both the inviter and invitee," he added.