The global engineering and consultancy firm Aurecon has severed a longstanding business relationship with the Adani Group, amid ongoing efforts by anti-coal activists to target firms working for the Indian conglomerate’s Australian mining arm.

Adani Australia released a statement on Wednesday saying it was “surprised” by the decision but that the “concerted campaign” against the Carmichael project by environmental groups had not succeeded, and that construction of the central Queensland thermal coalmine was under way.

But the decision is likely to buoy activists groups’ efforts to convince other major contractors to walk away. Their current focus is on another engineering consultant, GHD, which is working on the design of the mine.

Julien Vincent, the executive director of Market Forces, an investor action group, said the stance taken by Aurecon “certainly doesn’t surprise us”.

“Adani’s Carmichael coalmine project, along with the company’s corporate record make it brand kryptonite for any company that they are associated with,” Vincent said. “Aurecon joins a long list of companies to have walked away form the Carmichael project, or ruled out providing financial support to Adani’s dirty coalmine.

“We’ve found many people working in engineering firms want to participate in projects that advance a technologically advanced, sustainable economy. It should surprise nobody that employees at companies like Aurecon would want to disassociate from companies like Adani that are trying to exacerbate that crisis.”

In its statement, Adani said it was already in discussions with other businesses who had expressed an interest in taking on Aurecon’s work or other opportunities with the company.

“While we are surprised by the decision, given the positive long-term relationship and the fact that we are not aware of any commercial issues or disputes between our companies, we value the work that Aurecon has delivered for our port and renewable energy businesses.

“There has been a concerted campaign by extremists against our Carmichael project and businesses that partner with us. It has not succeeded and construction of the Carmichael project is well and truly under way.

“We have repeatedly demonstrated that we will not be intimidated or deterred from delivering on our promises to Queenslanders, Australians and the people in developing nations who desperately need affordable energy to help lift them out of poverty.”

Aurecon had not been directly involved in the Carmichael mine – it had been the engineering, procurement and construction contractor at the Abbot Point coal terminal since 2005. Adani bought the terminal in 2011.

This month environmental groups, including those using civil disobedience tactics, held a week of action targeting GHD in an attempt to convince the company to stop working with Adani.

There are relatively few engineering firms with the capacity to design and build Carmichael. Another global firm, AECOM, had been designing a railway between Carmichael and Abbot Point, but walked away amid a financial dispute. A deal with integrated services firm Downer EDI collapsed in 2017 after the company was pressured by activists.

Firms who do work with Adani are likely to be pressured by staff, shareholders, business partners and financiers, as well as outside activists.

Last week Engineers without Borders ended a longstanding partnership with GHD.

According to its 2018 financial report, GHD holds “multi-option, multi-currency facilities” with both Westpac and HSBC, two financial institutions who have policies ruling out financing the Adani Carmichael coalmine.

Market Forces says it would be “shameful” for companies to promote policies banning finance for thermal coal but to effectively do so through backing contractors to projects.

“Customers and shareholders will be furious to learn that they are financially connected to this environmental disaster,” said a Market Forces campaigner, Pablo Brait. “If Westpac and HSBC have any regard for their own commitments, they will either cancel their line of credit to GHD or convince the company to drop Adani’s dirty coalmine.

“We urge all banks and insurance companies that have pledged to avoid the Adani Carmichael project to closely examine who Adani’s business partners are, as there is a risk they could be funding this destructive project indirectly.”