(Bloomberg) -- An Adler Group SA bondholder has filed a suit in a Frankfurt court in a bid to thwart the company’s plan to restructure its debt in the UK.

The suit seeks an order declaring the effort to overhaul its debt under English law illegal, two people familiar with the case said. The action is at an early stage, said the people, who asked not to be named as the filing isn’t public yet. 

The identity of the plaintiff hasn’t been disclosed. A spokeswoman for the Frankfurt court couldn’t comment. A representative for Adler didn’t return calls and emails seeking comment.

The lawsuit could throw a spanner in the company’s efforts to extend debt maturities, relax audit deadlines and raise new loans by the end of next month.

The German real estate company has been negotiating for months with its creditors after it was targeted by a short seller and hit by a slowdown in domestic property transactions. After failing to get enough support from bondholders to meet German law requirements, Adler created a new UK-based unit to restructure its debt in London. 

Read more: Adler’s ‘Unfair’ Debt Deal Challenged by Investment Funds 

English law allows for judges to make restructurings binding also for dissenting creditors under certain conditions. Foreign companies can also apply as long as they have a sufficient connection to the country. 

The London proceedings started last month with DWS Group, Attestor Capital, Strategic Value Partners and Carval Investors opposing the deal agreed with a separate group of creditors. 

The dissenting group argue the plan treats certain investors unfairly. Bondholders are set to vote on the restructuring plan later this month, and the London restructuring process should complete by the beginning of April. 

--With assistance from Laura Benitez.

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