Credito Real defaulted on a 170 million Swiss franc ($175.98 million) bond last year, kicking off a commercial liquidation process in Mexico criticized by shareholders for lacking transparency.

The legal letter, dated May 23 and seen by Reuters, references a clause under Mexican law which allows any shareholder to demand a general assembly after two years.

Signed by Alvaro Martinez - a shareholder and representative of the minority holding group - the letter outlines several requests for the assembly, including getting access to Credito Real's financial statements over 2021 and 2022.

This includes getting details into the covert settlements Credito Real made with secured lenders - mainly large Mexican banks - as well as a thorough audit of the remaining funds.

The group's lawyer, Teodoro von Harrsch, said that Credit Real is now legally obligated to hold an assembly, and that "if they don't, we will go to a judge."

Credito Real, which offered payroll lending and unsecured credit, did not reply to a request for comment.

The demand for an assembly comes as Credito Real attempts to end a legal battle with a bondholder group that took it to court in Delaware to force them to undertake U.S. bankruptcy proceedings instead of in Mexico.

Credito Real has offered the group a deal to restructure over $1.9 billion in bond notes, a Delaware bankruptcy court heard Monday. It will need a majority of unsecured creditors in the next 60 days to sign off on it.

Reuters reported last year that talks between the group were taking place and that negotiations for a settlement were viable.

Von Harrsch said the deal "offers nothing to shareholders" and his group will keep pushing for transparency.

Last year, another group of foreign bondholders - collectively owed around $2 billion - were weighing fresh legal action against the company and its auditors in Mexico, to claw back some lost funds.

Some of those bondholders have since said they have lost hope and sold their bonds, facing an uphill battle as the most exposed unsecured creditor group.

(Reporting by Isabel Woodford)

By Isabel Woodford