"The investigation is being discontinued because the evidence collected was insufficient to justify prosecution," the Ottawa-based watchdog said in a statement, adding that it cooperated with enforcement agencies in numerous jurisdictions at part of its probe.

The investigation, which the bureau said began in early 2011, is one of several by global regulators into whether banks manipulated rates to boost derivatives prices.

The decision to drop the probe comes just a month after European antitrust investigators slapped a record 1.7 billion euro ($2.3 billion) fine on six U.S. and European financial institutions, bringing the tally of penalties related to the rate-rigging scandal to almost $6 billion.

EU regulators have said their probe is ongoing.

The Canadian investigation looked into London-based broker ICAP, as well as Royal Bank of Scotland (>> Royal Bank of Scotland Group plc), Deutsche Bank (>> Deutsche Bank AG), and the Canadian investment banking arms of JP Morgan Chase (>> JPMorgan Chase & Co.), Citigroup (>> Citigroup Inc) and HSBC (>> HSBC Holdings plc).

($1 = 0.7346 euros)

(Reporting by Cameron French; Editing by Jeffrey Hodgson, Bernard Orr)