SYDNEY (March 15): The Singapore-based son of Australian Prime Minister Malcolm Turnbull has claimed that he exposed alleged misconduct by Goldman Sachs in its dealings with 1Malaysia Development Berhad (1MDB), adding a further twist to the scandal involving the Malaysian sovereign wealth fund.

Mr Alex Turnbull, who is based in Singapore and manages a hedge fund, said he was sidelined and then resigned while working for the global investment bank Goldman Sachs in Singapore, after raising concerns about a deal that raised around US$6 billion in loans for 1MDB.

The explosive claims were dismissed by Goldman Sachs and threatened to overshadow upcoming talks between the Australian and Malaysian leaders at an international summit in Australia this weekend.

Mr Turnbull, who lives in Singapore with his Hong Kong-born wife Yvonne Wang, or Wang Yiwen, and their daughter, claimed he expressed concerns about the way in which billions of dollars in bonds were being raised by Goldman Sachs while he worked for the bank's special situations group in 2012 and 2013.

He resigned from the bank in 2014 and set up his own Singapore-based hedge fund, Keshik Capital.

Describing himself as a whistleblower, Mr Turnbull said he was "B-tracked" at Goldman Sachs after raising the concerns in an e-mail.

"When the 1MDB deal was done with Goldman I sent an e-mail to some of my colleagues saying, 'The pricing is nuts, what is the use of funds?'" he told The Australian newspaper.

"And I got a talking-to by compliance."

The deals allegedly brought in US$593 million for Goldman Sachs and were part of a scheme in which, according to the United States Justice Department, Malaysian figures including Prime Minister Najib Razak illegally received billions of dollars from the state fund. Mr Najib has denied any wrongdoing.

The claims by the Australian Prime Minister's son about his whistleblowing first surfaced on a Malaysian blog in which he apparently said that the allegations "will all come out" in a book called Billion Dollar Whale. The book, written by two Wall Street Journal reporters, is due to be published in September.

Mr Turnbull told Fairfax Media last week he was misquoted by The Australian but would not comment further. He was unable to be reached by The Straits Times.

Goldman Sachs rejected his claims, saying it had found no electronic evidence of Mr Turnbull raising concerns about its dealings with 1MDB.

"Mr Turnbull had no involvement in the 1MDB transactions," the bank told The Australian Financial Review on Monday.

"Not surprisingly, we haven't found any electronic communications of Mr Turnbull identifying any improper conduct with respect to these transactions or any action taken against him as a result."

A copy of Mr Turnbull's resignation letter, obtained by The Australian Financial Review, apparently did not mention his concerns about 1MDB.

In Australia, Prime Minister Turnbull has refused to discuss his son's comments.

The Prime Minister is due to meet with Mr Najib at a special summit this weekend between Australia and leaders from the Association of South-east Asian Nations. It will be the first time Australia has hosted a summit with Asean leaders.

Asked whether the affair could damage his relationship with Mr Najib, Prime Minister Turnbull told reporters last week: "No. No. No. I'm not going to, I'm not going to comment on it."

Malaysia's former prime minister, Dr Mahathir Mohamad, now a leader in the opposition, urged Mr Turnbull to raise the 1MDB scandal with Mr Najib at their upcoming meeting.

Dr Mahathir said Mr Alex Turnbull should discuss what he knows with the various international authorities investigating the 1MDB scandal.

"He must be willing to divulge to the right authorities - whether it is the Monetary Authority of Singapore, the US Department of Justice or the Malaysian Anti-Corruption Commission even," Dr Mahathir told The Australian on March 9.

"He should not hide what he knows, but it should not be done out of spite...only to reveal the truth."