A consumer advocacy group has lodged a formal complaint with the Australian Competition and Consumer Commission (ACCC) about Qantas' flight credit policy.

Choice said the airline's flight credits scheme was "unfair and unworkable" and it might involve "potential unfair contract terms and misleading and deceptive conduct".

Choice spokesperson Dean Price said Qantas was placing unreasonable barriers in the way of travellers trying to redeem their credits or get a refund from cancelled travels.

"The Qantas flight credits system is currently unworkable for most customers."

Mr Price added that one of the key problems many passengers faced when trying to use Qantas credits was they could only use credits for flights that cost the same or more than their original fare if they originally booked after September 30, 2021.

The Qantas confirmed the value of outstanding flight credits was $1.4 billion and the airline had extended the validity of the majority of flight credits which could be used for travel up until the end of 2023.

"We did put some fare rules back last September when borders began to stabilise which means customers can choose not to take a flight and still retain that value in a flight credit, but it does need to be used on a new booking of equal or higher value," a spokesperson told the ABC.

The ABC previously reported that some Qantas passengers said they were worse off when redeeming a credit and they accused the company of "price gouging".

But Qantas CEO Alan Joyce rejected the allegation, saying customers "get the exact same as what you paid for".

Choice has asked the ACCC to investigate whether Qantas has breached the misleading and deceptive conduct provisions under section 18 of Australian consumer law.

It has also asked the consumer watchdog to examine if misleading and deceptive conduct has occurred in relation to the treatment and communications about flights sold to customers.

The ACCC told the ABC it would consider the information provided by Choice as part of its ongoing investigation.

"This has included seeking information over the past few weeks from consumers about their experiences using Qantas flights credits."

One in four people have flight vouchers expire

Last month, a national report by Choice found 72 per cent of people had received a flight voucher due to COVID-19-related flight cancellations.

However, more than one in five people (21 per cent) had been unable to use their vouchers after their flights were cancelled due to COVID.

One in four people had flight vouchers expire before they could use them.

The consumer group has called for a mandatory information standard, with clearer terms and conditions, for all travel service providers.

"A simpler and more accessible system for re-booking flights and getting refunds would assist customers to get value from the money they have paid to the company — whether that is a flight or a refund," Mr Price said.

The NSW government is currently considering such a standard.