ANZ and Commonwealth Bank have reached agreements with plaintiffs involved in a United States class action over alleged manipulation of the bank bill swap rate.

In separate announcements yesterday, the two banks said they had reached settlements “without admission of liability”. Both settlements are still subject to negotiation of the terms, execution of a deed of settlement and court approval.

Westpac reached a settlement last October.

A NAB spokesperson said claims against the bank were dismissed in February last year.

The class action was launched in 2016 and involved 17 banks and two global broking houses.

The plaintiffs claimed that from at least 2003 the banks and brokers “co-ordinated manipulative transactions” during the rate fix window – the brief period during which rates are set each day.

They allegedly did this by “artificially increasing or decreasing the supply of prime bank bills” during the fix window. They were also accused of sharing information on their BBSW rate exposures.

The US class action followed court cases initiated by ASIC, alleging that each of the four big banks had rigged or attempted to rig BBSW for their own financial benefit.

In that case, ANZ, CBA and NAB provided enforceable undertaking to address their BBSW conduct, while Westpac took its case to court. The court ruled that Westpac had acted unconscionably but its traders did not manipulate the rate. The bank was fined $3.3 million and ordered to pay ASIC’s costs.