Parti Pribumi Bersatu Malaysia (Bersatu) Youth wing's invitation for Prime Minister Najib Abdul Razak to debate Dr Mahathir Mohamad was not a threat, said party president Muhyiddin Yassin.

Muhyiddin said as such, Umno Youth should not have blocked the Bersatu Youth members as they did yesterday.

"I don't think (the invitation) can be considered a threat or so on. (Umno Youth) should have been more gentlemanly," he said at a press conference in Parliament today.

Umno and Bersatu Youth members squared off at the Putra World Trade Centre yesterday when the latter came to send Najib an invitation to attend the "Nothing to Hide 2.0" forum.

Muhyiddin hoped that such an incident would not happen again.

The forum will be held at the Dewan Raja Muda Musa in Shah Alam, at 3pm on Aug 13.

During the forum, Mahathir plans to grill Najib about how the latter received RM2.6 billion in his personal accounts.

Mahathir had claimed that the sum was stolen from 1MDB.

Najib, however, has consistently denied such allegations, claiming that the sum was a donation from the Saudi royal family.

Attorney-general Mohamed Apandi Ali has affirmed this and cleared the prime minister of any wrongdoing.

The previous "Nothing to Hide" forum was held at Umno’s headquarters at the Putra World Trade Centre, Kuala Lumpur.

It was organised by law-based NGO SukaGuam as a platform for civil society groups, including Mahathir, to grill Najib. Najib had supposedly agreed to appear at the forum.

However, Najib did not turn up and Mahathir took to the stage instead to address the audience of about 2,000 people until the police stopped him from continuing his speech.

Police at the time cited security concerns as the reason for cancelling the forum.

Inspector-general of police Khalid Abu Bakar claimed Najib was unhappy with his move to have the event cancelled, but said he persisted for the sake of safety and security, as well as to preserve harmony.