Prime Minister Najib Abdul Razak can put to rest the controversial allegations that he had taken US$700 million (RM2.6 billion) in state funds by simply showing his bank accounts, former prime minister Dr Mahathir Mohamad has said.

"When people charge him with something, he says it is a plot. Nonsense, it's not true. Prove that it is not true. It is very easy for him to prove it is not true.

"He has these bank accounts, all he has to do is say: 'you examine my accounts, you look at it'," Mahathir said in an interview with UK-based BBC that was aired this morning.

This is the first time Mahathir publicly weighed into Najib's position after The Wall Street Journal (WSJ) reported last Friday that US$700 million of 1MDB's funds was deposited into Najib's private bank accounts with Ambank.

Najib has since denied that he had taken government funds for personal gain and accused Mahathir of working "hand in glove" with foreigners to create a political crisis.

He also accused Mahathir of wanting to oust him for not fulfilling his wishes.

However, Mahathir said mere denials were insufficient.

"The proof in the pudding is in the eating. You say you deny, but let's see the accounts," he said.

‘All this is about money that has been borrowed’

Mahathir also denied that he was working with the foreign media to make allegations against Najib.

"All this about the money that had been borrowed and all these shenanigans that followed - is something that I read in the foreign press and I confirmed by asking local people.

"I did not work with the foreign press," he said in the interview.

Mahathir also addressed accusations that he was out to oust Najib for not following his wishes, stating that the prime minister had made some promises to him but that they were "minor things".

"I didn't ask him why he didn't do what he promised to do, which is to build the (crooked) bridge and continue the railway line.

"That is a minor thing to me, if you don't want. Every prime minister has a right to have his own policies," he said.

Mahathir has been Najib's fiercest critic over his handling of the Finance Ministry-owned 1MDB, which has accumulated RM41.8 billion in debt. Najib is also finance minister.