Millions of Australians may be able to claim a refund on some Nurofen painkiller products if a class action against the drug's makers is successful.

Key points: ACCC prosecuted company over four products for containing same ingredient

ACCC prosecuted company over four products for containing same ingredient Fine could be as high as $6 million

Fine could be as high as $6 million Law firm representing consumers could get damages in the hundreds of millions of dollars

Lawyers for pharmaceutical giant Reckitt Benckiser admitted today in court that the company had engaged in "deceptive and misleading" behaviour by advertising that four products could treat specific types of pain.

The company now faces a multi-million dollar payout.

Peter Moore, one of the named plaintiffs in the class action against the British pharmaceutical giant, said he had previously used Nurofen for a number of issues.

"I had a back operation in 1992 that went wrong and last year my bank went out twice ... and I was crawling around the floor basically and instead of taking Panadeine Forte all the time, I went and got Nurofen, which says for back pain, and it didn't do anything for my back," Mr Moore said.

The product in question, Nurofen Back Pain, had been marketed as providing "targeted relief".

Mr Moore said he had suffered from HIV for over two decades and to deal with one of the symptoms he tried using Nurofen Migraine Pain.

"And they did nothing for me," he said.

Last year, the Australian Competition and Consumer Commission (ACCC) successfully prosecuted Reckitt Benkiser over four products: Nurofen Migraine Pain, Nurofen Tension Headache, Nurofen Period Pain and Nurofen Back Pain.

Each product claimed to target specific pain, when in fact it was found that they all contained the same amount of the same active ingredient, ibuprofen lysine.

Next week, Reckitt Benckiser will learn how much it is being fined over that matter. The ACCC wants them to cough up $6 million.

Class action will bring consumers direct compensation

However, $6 million could be small change for the company, compared to another class action being led by Bannister Law, who are representing angry consumers like Mr Moore.

Diane Chapman, a solicitor with the firm, said the ACCC had taken an action on the basis of the product being misleading to consumers.

"In that case consumers aren't directly compensated, so we've taken up the case on behalf of the consumers to seek compensation for them directly," Ms Chapman said.

Ms Chapman said that if the case was successful, any Australian who purchased one of the products would be eligible for a refund.

"We're either going to ask for receipts or for statutory declarations, so once the matter is settled and if there is a compensation pool, we will contact anyone who has registered on our website and ask them to either provide them with a standard statutory declaration that we will send them or with the receipts," she said.

Today was the first hearing between Bannister and Reckitt Benckiser.

Ms Chapman said the company admitted the product was misleading and deceptive.

"So we are seeking a hearing later this year," she said.

Even though the company had admitted that, Ms Chapman said that there would still be a legal argument based on quantum, which is the amount to be compensated.

"We need to really make sure that we go to hearing to be confirmed that we have won the case, but we are more confident from the hearing this morning that it is likely that consumers will be compensated."

If successful, damages could run into the tens and possibly hundreds of millions of dollars.

So far, however, it has had little effect on the share price of the company, which is valued at over $80 billion.

Reckitt Benkiser was contacted by the ABC for comment.