The investigation into the alleged market manipulation by ANZ’s bond traders is of the “highest priority”, says the top corporate regulator, citing the seriousness of the misconduct and the potential cost to taxpayers if borrowing costs had been forced higher.

Joe Longo, the chairman of the Australian Securities and Investments Commission, told a parliamentary joint committee in Sydney on Friday that the high-profile investigation into ANZ’s role in a $14 billion government bond sale had been expanded to include misreporting of data.