Xstrata Coal's $186 million of investment in early works and exploration in Queensland, including the $6 billion Wandoan coal project, has resumed after the announcement of a revised resource rent tax, according to the company.

Xstrata Coal chief executive Peter Freyberg, who helped negotiate the minerals resource rent tax (MRRT), said the result of last week's discussions had brought reassurance for investment and aided in keeping the industry's international competitiveness.

''[This] decision effectively lifts the suspension on expenditure announced by Xstrata last month and allows the next stage of planning for this internationally significant Wandoan project to proceed,'' he said.

A final investment ruling on the Wandoan coal project in Queensland's Surat Basin is anticipated in the second half of 2011.

While Xstrata restarted its Queensland projects, its fellow mining tax negotiator BHP Billiton told shareholders the full effect of the revamped levy was still cloudy.

According to BHP chairman Jac Nasser, the new tax regime is ''a good foundation'' on which ''an effective tax can be implemented''.

''There is still a great deal of detailed work to be done before this tax is enacted and its impact is certain.''

''We will work with the government to ensure that the final outcome of the minerals taxation proposal maintains the international competitiveness of the Australian resources industry and is in the long-term interests of all Australians,'' Mr Nasser said.

His comments came as Resources Minister Martin Ferguson addressed members of the Queensland Resources Council in Brisbane, where the latter rejected suggestions that the government had miscalculated its $12 billion tax.

According to the resources minister, last week's Australian Bureau of Agricultural and Resource Economics update on rising commodity prices had been considered into the $10.5 billion MRRT.