KUALA LUMPUR - Malaysian Prime Minister Najib Razak took a swipe at his fiercest critic Mahathir Mohamad, saying he had never imagined that the former premier could be so critical of his administration.

"Never in my wildest dreams did I imagine that one of my predecessors would be against me in this manner,'' Malaysiakini quoted Mr Najib as saying on Thursday at the opening of the World Capital Markets Symposium.

"He is no longer a prime minister and should not take centrestage," he said, drawing laughter from the audience

While Mr Najib did not mention Dr Mahathir in his speech, it was obvious that he was referring to the elder statesman.

Dr Mahathir has been highly critical of Mr Najib in the past months, particularly on the issue of debt-ridden state investor 1Malaysia Development Berhad (1MDB).

The former prime minister had raised eyebrows when he attended the Bersih 4 rally over the weekend. The protesters, among other things, demanded the resignation of Mr Najib over allegations that US$700 million (S$990 million) was deposited into his personal bank accounts.

The Malaysian leader has denied any wrongdoing.