SINGAPORE - Noble Group Ltd, Asia’s biggest commodities trader, said it has hired PricewaterhouseCoopers (PwC) to review the way it values some of its assets - its biggest move yet to boost transparency after an attack on its accounting practices. Allegations by little known Iceberg Research in February that Noble was inflating its assets by billions of dollars have wiped 40 percent off the Singapore-listed firm’s market value. A cut by Standard & Poor’s to Noble’s credit rating outlook last month that cited concerns about the valuations of long-term supply contracts has also hurt. Noble, which has rejected Iceberg’s allegations, has sought to reassure investors, providing more details on its fair value accounting of assets and starting legal action in Hong Kong against a former employee it had fired in 2013 and who it has said is linked to Iceberg. In this new audit - which is separate from work done by its regular auditor Ernst & Young - PwC will review Noble’s mark to market accounting models and governance framework. The company said the appointment was made by a newly established committee of four non-executive independent Noble board members. “What some people are saying is that mark to market is still a big black box. So they are trying to be more transparent,” said Carey Wong, an analyst at OCBC Investment Research. A spokeswoman for Noble said the review will take “weeks not months.” After the review, PwC will issue a report to the board and a summary will be released. Responding to the announcement, Iceberg Research called for PwC to do an in-depth review of all valuation models used by Noble. Shares in Noble climbed 3.5 percent on Tuesday, giving the commodities trader a market value of S$4.95 billion ($3.7 billion). Other moves taken by Noble to rebuild confidence include the appointment of new board members and a share buyback. Last week it redeemed its 2020 bonds at their earliest call date on the same day its 2015 bonds matured - a total payout of $735 million to creditors that underscored it had no problems with liquidity. Richard Elman, Noble’s biggest shareholder with about a fifth of its shares, has urged investors to have confidence in the firm while China Investment Corp, Noble’s second-largest shareholder with a 9 percent stake, has said it would support Noble’s business.