Prime Minister Najib Abdul Razak's aide Tengku Sariffuddin Tengku Ahmad has challenged DAP leader Lim Kit Siang to "admit to his alleged ambition" of wanting to be deputy prime minister.

"Lim needs to come clean on this, as it is the right of Malaysians to know who they will be ruled by if they vote for Pakatan (Harapan).

"He must tell the people whether it is his political ambition to be the deputy prime minister, as confessed by Mahathir on Jan 19, 2017," said the press secretary in a statement today.

Previously, Mahathir said he actually meant "MCA" that sought the DPM post in 2009, and had mistakenly mentioned "DAP" during a talk.

On Monday, MCA deputy secretary-general Loke Yuen Yow said he had proposed the creation of a DPM II post to be filled by MCA in 2009, but stressed the suggestion was made in his personal capacity.

The prime minister, however, said MCA never sought the DPM post.

Loke's explanation did not assuage Tengku Sariffuddin, who said DAP must clarify this because it has the largest number of parliamentary seats in the Harapan alliance.

He also asked if this was the reason Lim was trying to be nice with PAS.

Lim had come under fire for saying he is willing to negotiate with PAS to ensure a greater opposition coalition in the next general election.

In response, the Gelang Patah MP said he is even willing to work with BN for Malaysia's benefit.