“If our understanding of what was said … at the investor meeting is correct, Bell Rock is concerned that the market is misinformed as to whether or not [Whitehaven] is bidding for one or both mines and what implications this may have for the share buyback program,” it reads.

“In our view, if our understanding is correct, this information may have a material effect on the price or value of WHC’s shares and should be disclosed immediately … if not disclosed, there is a material risk that a false market in [Whitehaven]’s shares is being created due to the uncertainty surrounding these media reports and selective disclosure about these matters that may have been made to some but not all shareholders.”

Whitehaven declined to comment.

Bank of America has already downgraded its assumptions of Whitehaven’s buyback program from 30 per cent of profit to zero for this and the next financial year, while Barrenjoey told clients that while it was “not opposed to an asset acquisition … it will come down to price”.

Whitehaven is far from the only group interested in the two BHP mines, with The Australian Financial Review’s Street Talk column reporting other shortlisted parties include Yancoal Australia, Coronado Global Resources and BUMA Australia. The sale is being conducted by Macquarie.

As the Financial Review has previously reported, the London-based hedge fund had earlier written to Whitehaven raising concerns about a “general lack of clarity around [the company’s] growth and expansion plans”.

Bell Rock, according to its latest letter, is also seeking clarification on the remediation cost that come with the Blackwater mine, including assurances that it will not replicate the sale of BHP’s Mount Arthur mine, “where bidders were asked to pay at least $700 million for … remediation”.

“Mt Arthur provides a cautionary tale for [Whitehaven] and we believe the board needs to have regard to shareholder value in deciding whether or not to pursue the potential acquisition [of the BHP mines],” the letter reads.

Whitehaven shares closed 4 per cent higher at $6.67 on Friday. However, they have slumped more than 10 per cent in the last month.