Prime Minister Najib Abdul Razak has been dared to accept Dr Mahathir Mohamad's debate challenge, and prove he's "not a liar".

PAS vice president Tuan Ibrahim Tuan Man said accepting the challenge will give Najib the chance to prove who is right and who is wrong.

"Najib should debate Mahathir after the former prime minister announced his willingness and accused Najib of 'never speaking the truth, always lying'.

"This is Najib's chance to prove who is actually lying, him or Mahathir, especially after his former boss was just proven to be wrong on the resignation of the parliamentary speaker," Tuan Ibrahim ( photo ) said in a statement today.

He was referring to Mahathir's announcement that speaker Pandikar Amin Mulia would be resigning from his post, which the latter has since denied.

Mahathir said this during a speech in Ipoh yesterday, in which he claimed the prime minister has been peddling lies, especially concerning the purchase of a new government jet.

At the same event, he also said he was willing to face Najib in a public debate .

'Clear air on 1MDB'

Tuan Ibrahim said the debate is especially necessary after the prime minister said yesterday that 1Malaysia Development Berhad's (1MDB) RM42 billion debt is actually locked into the Tun Razak Exchange (TRX) and Bandar Malaysia projects.

"If what Najib said is true, then this is an admission that 1MDB has used up the RM42 billion loaned to it, and it is now forced to rely on development of TRX and Bandar Malaysia.

"Isn't this a smash shot for Mahathir to say that his allegations about 1MDB all this while is true?" he posed.

The former premier has repeatedly demanded answers regarding 1MDB's finances, and why it was so heavily in debt.

It is part of his campaign to oust Najib, although the latter has refused to budge and has vowed to stay on as prime minister.