PETALING JAYA (THE STAR/ASIA NEWS NETWORK) - Prime Minister Datuk Seri Najib Razak said that it was "not proper" for him to publicly debate with Tun Dr Mahathir Mohamad at the cancelled 1Malaysia Development Berhad (1MDB) dialogue last Friday.

"The function changed from a closed-door dialogue to an open debate. This would have caused an open political confrontation between Mahathir and myself," said Najib in a blog post on Wednesday.

"It is not proper for a debate like this to be held openly with the former prime minister who is also from the same political party," he said.

Najib said that him debating with Mahathir would not bring any benefit to their Umno party and the ruling Barisan Nasional ruling coalition.

"As prime minister and Umno president, I am responsible to safeguard the good name of the government and party," he added.

However, Najib said that Mahathir had the right to ask questions and he was willing to explain to the former prime minister.

Najib said that he regrets that the event had to be cancelled for "security reasons" and that it is still his intention to have a dialogue session in the near future with the NGOs who were invited.

The scheduled dialogue between Najib and NGOs on the subject of 1MDB was cancelled following a Twitter message by the Inspector-General of Police Tan Sri Khalid Abu Bakar saying that public safety was threatened.

Mahathir, who showed up at the dialogue session, went up on stage to address the crowd but was told by police to stop speaking five minutes into the speech.