LONDON (REUTERS) - Standard Chartered has referred allegations of impropriety at an Indonesian power company that the bank's private equity arm invested in to the appropriate authorities, the bank said on Tuesday.

The Wall Street Journal earlier reported the bank faced an investigation by the US Department of Justice into whether StanChart failed to stop alleged misconduct at MAXpower Group, a power plant builder.

"Standard Chartered takes very seriously allegations of impropriety in any of our private equity investments. We proactively referred this matter to the appropriate authorities and have conducted our own review," a spokesman for the bank said in an emailed statement.

MAXpower said the allegations gave a "one-sided and partial view of the operations and events at MAXpower and as such do not give a full, or true view."

"Since the restructuring of the company's shareholding and management in mid-2015, the company has implemented robust remedial actions including enhanced internal controls," it added. "We have engaged and continue to work with professional advisory firms to fully investigate issues and questions that have been raised. Accordingly, it would be inappropriate for the company to comment further at this stage," it said.

The allegations could add to StanChart's legal concerns, and come as it awaits a decision from US authorities over whether it will remain under supervision for several more years over lapses in Iran-related anti-money laundering efforts.

Under a deferred prosecution agreement it reached with US authorities in 2012, StanChart is due to remain under supervision by an independent monitor until the end of 2017.

Sources have said the bank now expects that date to be extended, possibly by several years.