The results for the first half of the 2019-20 financial year were announced by new chief executive Mike Henry and were broadly in line with market expectations.

Although coal remains one of BHP's major "pillars", the focus is on coking coal from Queensland, used in steelmaking, rather than its thermal mines for power stations at Mount Arthur and Cerrejon in Columbia.

Mount Arthur has been the focus of considerable unrest about the use of casual mineworkers on substantially lower rates and conditions than their directly employed counterparts, and the BHP results coincided with Attorney General Christian Porter telling employers to "get their houses in order" over "wage theft", which he described yesterday as "an endemic problem" in Australia.

Mr Porter and other senior Coalition figures have met with disaffected Mount Arthur workers in recent months and listened to their concerns.

The government's announcement also coincided with supermarket company Coles adding its name to the list of businesses with serious underpayment issues, reporting a $20-million provision to cover "unintentional" underpayment of some staff stretching back for six years.

One Nation Senator Malcolm Roberts has taken the "wages theft" argument up to the government, and yesterday accused BHP of "unlawful, immoral and unethical behaviour" as a business strategy at Mount Arthur.

A BHP spokesperson declined to comment on Mr Robert's statement.

But the Australian Industry Group, normally a supporter of the Coalition government, has criticised Mr Porter's proposal to introduce criminal penalties for what it describes as "serious underpayments" of workers.

AIG says that while criminal penalties "might seem like a good idea at first glance", they would further discourage people from starting businesses and could lead to under-paid workers waiting "years" for court cases to be concluded before they received any money.

BHP's nine Queensland mines had underlying earnings before income tax of $US728 million ($1.08 billion) on revenues of $US28 billion ($4.23 billion) for the six months to December 31.

Its NSW Energy Coal division, which includes earnings from its share of the Newcastle Coal Infrastructure Group coal loader on Kooragang Island, recorded an underlying before-tax loss of $US94 million ($140.5 million) on revenues of $US480 million ($717 million).

In a different measure, the energy coal division had an "underlying return on capital employed" or ROCE of minus $US152 million ($227.5 million) in "annualised profit excluding net finance costs and exceptional items" for the six months to the end of 2019.

This contrasted with an ROCE of $US195 million ($291 million) for the corresponding six months the previous year.

The results reported an average price for thermal coal of $US58.55 ($87.50 a tonne), down from $US84.15 ($125.75) a year before.

At the same time, Mount Arthur reported increased production costs at almost $US60 ($89.60), a tonne, up from $US46.00 ($68.75) a year ago - a result that may be linked to BHP's acknowledged shift from casual to more permanent employment at the mine.

BHP now has three types of employees at Mount Arthur all engaged as mineworkers on substantially different rates of pay and conditions.

The lowest earners are casuals employed through contractors such as Chandler Macleod, followed by permanent workers engaged through BHP's Operations Services unit, and mineworkers directly employed on BHP's Mount Arthur enterprise agreement.

BHP said in its results yesterday that it now had more than 1500 people employed through Operations Services in its Australian iron ore and coal businesses, including Mount Arthur.

BHP has also confirmed selling some of its shareholding in the NCIG loader to Whitehaven, saying it had spare capacity and also exported through the other loader operator, Port Waratah Coal Services.

The BHP spokesperson said the reduction in its stake from more than 35 per cent to less than 28 per cent was not done to reduce the company's exposure to thermal coal.

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