Malaysia is blocking the Australian government's requests for information over a corruption scandal which may involve the country's Prime Minister, Najib Razak.

Fairfax Media understands that senior officials in Canberra are aware of intelligence that implicates people in the offices of both Mr Najib and his predecessor, Abdullah Badawi, in allegedly improper dealings involving two Australian Reserve Bank firms over contracts to print polymer bank notes.

But Malaysia has ignored a formal mutual assistance request from the Commonwealth Attorney-General's Department to hand over sensitive information about the financial dealings of a group of Malaysian middlemen embroiled in Australia's most important bribery case.

The Malaysian middlemen are allegedly implicated in the bribery scandal, which has sparked the ongoing prosecution of several Australian businessmen who worked for two RBA firms – Securency and Note Printing Australia. 

In another sensational development linked to the case, an Australian judge has accused WikiLeaks of blatant criminal conduct in publishing online last year a suppressed court order naming Mr Najib. It's also been revealed that WikiLeaks is under federal police investigation for the breach.

​The RBA bribery scandal involves allegations that Malaysian officials were to be bribed as part of a scheme by the two Reserve Bank companies to win contracts to turn Malaysia's currency from paper notes to polymer between the late 1990s and 2009.

Fairfax Media can reveal that the scandal is particularly sensitive in Malaysia because some of the allegedly corrupt middlemen are suspected of having close dealings with figures in the offices of both Prime Minister Najib and his predecessor, Abdullah Badawi.

It's understood that while he was deputy prime minister, Mr Najib's office was allegedly used by a middleman to negotiate a kickback from one of the Reserve Bank firms.

A representative for Mr Najib has dismissed the claims and is threatening legal action. The information about Mr Najib and Mr Badawi is not derived from the Australian court proceedings, but from an ongoing investigation by Fairfax Media involving high-level sources across Australasia.

However, on Tuesday afternoon, Victoria's Supreme Court revoked a suppression order obtained last year by Australia's Department of Foreign Affairs and Trade and which names Mr Najib.

The court order had prevented the publication of any information aired in ongoing Reserve Bank bribery court proceedings that "reveals, implies, suggests or alleges" that "Mohammad Najib Abdul Razak, currently Prime Minister (since 2009) and Finance Minister (since 2008) of Malaysia" ever "received or attempted to receive a bribe or improper payment".

The order also prevented the naming of former prime minister Badawi and several top politicians from Indonesia and Vietnam, where bribes were also allegedly paid by RBA firms to win contracts. 

The court had initially agreed a suppression order was necessary to avoid unfairly implicating foreign leaders who were not being formally accused of any wrongdoing and in order to protect Australia's "national security" and "to prevent damage to Australia's international relations".

"DFAT's concern was that the publication of the suppressed information, in relation to the named persons [who include Mr Najib], would offend or embarrass them in circumstances that may have adverse consequences for Australia," Supreme Court Justice Elizabeth Hollingworth said in a recent finding. 

But in revoking the order, Justice Hollingworth said the earlier online publication of the suppression order by WikiLeaks meant that any ongoing attempt to keep secret its contents was futile. 

The judge also revealed that the federal police "are investigating conduct of WikiLeaks and whoever supplied the DFAT order to WikiLeaks". 

The judge said the online dissemination of the order by WikiLeaks, which is headed by Julian Assange, was "a clear and deliberate breach of law" that was also accompanied by a WikiLeaks press release "full of sensational, inaccurate allegations".

While the court has stressed that "none of the named persons [including Mr Najib and Mr Badawi] is a person whom the accused are alleged to have conspired to bribe", it is understood that the offices of both Malaysian leaders have been implicated in suspected corrupt dealings.  

No overseas politicians have been charged or formally accused of conspiring to receive bribes, with the prosecution case restricted to allegations that overseas central bank officials, rather than any ministers, were bribed between 1999 and 2004. This is despite evidence suggesting that alleged bribes were paid by the RBA firms until late 2009 and that overseas politicians may have been complicit in the scandal.  

One well-placed source said he was told informally by the federal police that the agency was told its investigation was "not to go certain places".

A prominent opposition MP said the Malaysian public deserved to know why Mr Najib or his representatives had personally met with officers from one of the RBA firms in Malaysia.

"These questions could not come at a more important time in Malaysia," said Rafizi Ramli, Secretary-General of the People's Justice Party, referring to a series of huge corruption scandals that threaten to engulf Mr Najib.

Mr Rafizi warned that "the Australian government will be seen as being complicit with Mr Najib in his effort to stay in power" if it went to further lengths to prevent disclosure of crucial information.

Fairfax Media has previously reported that a Malaysian middleman and former politician, Dato Abdullah Hasnan, sent an email to the RBA in November 2007 in which he stated he had "managed to personally convince my prime minister/Finance minister [Abdullah Badawi] and the Malaysian cabinet to accept and adopt the polymer bank note technology".

At the time of the email, Mr Najib was deputy prime minister and Mr Badawi was working alongside an alleged bribe payer.

Malaysia's failure to respond to the federal government assistance request in the bribery case underscores the flimsy nature of regional anti-corruption efforts, which are routinely undermined by politicians blocking investigations that threaten them or their associates.  

A well-placed Canberra source told Fairfax Media that Mr Najib's government had blocked the mutual assistance request because of the suspected involvement of top Malaysian officials.

The refusal from Malaysia has hampered efforts by the Commonwealth Director of Public Prosecutions to make its case that former senior executives from two Reserve Bank firms conspired to bribe Malaysian officials. The Attorney-General's Department declined to comment.

The Malaysian government is under further pressure from revelations last month from Fairfax Media that senior Malaysian officials were involved in in an unrelated bribery scandal involving the purchase of multimillion-dollar Australian properties. The properties were bought by a Malaysian government agency in return for kickbacks wired to Malaysian officials by Australian developers.

The Fairfax Media reports sparked raids by the federal police and the recent suspension of two top officials from Malaysian agency MARA, Datuk Mohammad Lan Allani and Datuk Abdul Halim Abdul Rahim. 

Malaysia's largest financial scandal, however, involves allegations that nearly $700 million from a sovereign wealth fund, 1Malaysia Development Berhad (1MDB), was siphoned into a private bank account in Mr Najib's name.

Mr Najib has said he did not take any funds for personal gain. Media outlets and bloggers have reportedly been threatened with legal action for reporting the allegations.