The pension provider embarked on the 26-month campaign in 2014 after it discovered it was in breach of superannuation laws requiring it to place customers' retirement savings in a no-frills, low-cost MySuper fund unless directed otherwise.

Rather than move each of the nearly 13,000 relevant members into the MySuper product, Colonial wrote to the members and urged them to act to ensure Colonial could continue to receive their super contributions.

Colonial claimed a recent legislative change required it to make contact and required it to hold investment directions.

Each of the three claims was false or misleading.

In calls with customers, its employees failed to mention it was required to transfer their accounts into a MySuper product if no investment direction was provided.

The conduct involved employees in senior management positions and drafts of the letters and calls' script being sent to watchdog Australian Prudential Regulatory Authority.

The fact Colonial approached APRA pointed away from a finding that Colonial "plotted" to make false or misleading statements, Federal Court Justice Bernard Murphy said on Tuesday.

He said the $20 million fine would have been higher if not for the financial institution's substantial remediation program to compensate members.

So far, about $67 million has been repaid to 5745 customers called using the offending scripts on the assumption they'd have moved to MySuper if never called.

A further $45 million to $53 million is expected to be paid to other affected members.

Colonial has also already paid $9.5 million to customers without assessing the nature of the calls received.

The wealth management group, which posted annual profits in excess of $200 million during the campaign, denied it was involved in a "deliberate and considered attempt" to further its own commercial interests.

But it didn't cavil with regulator ASIC's submission that the campaign effectively involved it "seeking to take advantage of members of FirstChoice Personal Super whose interests it was, as trustee of the fund, duty-bound to protect".

"It is important that Colonial, and other participants in the superannuation industry, are not left with the impression that the cost of courting a risk of contravention may be regarded as an acceptable cost of doing business," Justice Murphy said.

Colonial said it had put every effort in the past three years into improving quality and management oversight, and implementing regulatory reforms following issues raised in the banking royal commission.

"We have apologised unreservedly to members impacted by these historical issues and have taken action to fix past breaches including by compensating affected members, with interest," Colonial First State Superannuation chief executive Kelly Power said in a statement.

"As we finalise the process of establishing CFS as a standalone business, we are making significant investments to be a better business with members' interests at the heart of everything we do."

Australian Associated Press