A previously secret parliamentary hearing has been released, revealing that tobacco giant Philip Morris used the occasion to lobby for cheaper legal cigarettes.

The company was on Monday controversially called to give evidence to a Senate committee into the booming illicit tobacco trade.

However, the session was held in private, with the broadcast cut, much to the disappointment of anti-smoking advocates.

A uncorrected proof of the transcript seen by AAP reveals Philip Morris executives argued the crisis would lessen if the government dropped taxes on its products.

'Today, the tax on a legal $37.95 pack of 20 cigarettes is at least $34, while illicit cigarettes sell for half this,' the company representative, who had their name redacted, said.

'If the parliament wants to materially reduce illicit tobacco and bring consumers back into regulated channels, that gap must be narrowed.'

The same speaker also said that 'on almost any street corner you can find a packet of comparable illicit product for between $12 and $25'.

Philip Morris said it was 'very credible' that all legal sales of tobacco would be unfeasible by 2030 unless excise was lowered.

The Illicit Tobacco & E-cigarette Commissioner estimates the illicit market makes up 50-60 per cent of all tobacco sales, comprising $4-7 billion of sales.

Philip Morris argued the growth of the illicit market was driven by 'three forces acting together: price, access and enforcement'.

It argued that given four million Australians consume nicotine, it was better for public health, community safety and the government's budget if they did so legally.

'We are not here to contest public health objectives. We are here to provide evidence on where regulation is failing and what will restore regulatory control,' the speaker said.

Australian Council of Smoking and Health chief executive Laura Hunter said Philip Morris' testimony was 'like inviting mosquitoes into a hearing on malaria'.

'You had a tobacco giant warning about pressures on its business while profiting billions from products that kill 66 Australians every day,' she told AAP.

'You'd almost think their real crisis was their tax bill.'

Philip Morris has not responded to requests for comment.

The company's appearance in Canberra was controversial as the government and public health advocates believe it ran counter to an international treaty Australia signed up to in the mid-2000s.

However, the Liberal-controlled committee allowed the Philip Morris executives to give evidence, and granted it a closed-doors hearing.

South Australian Senator Leah Blyth, the committee chair, said it didn't 'make sense to have an inquiry into illicit tobacco and not hear from all entities impacted'.

After dissent from Labor and Greens committee members, it was agreed the transcript would be made public.

As of Thursday afternoon, it was yet to appear on parliament's website.

Philip Morris said it appeared before the Senate as a 'legal, taxed and regulated company working toward a smoke-free future'.