Allen & Overy (A&O) is suing a former client for $343,448 (£264,000) arising out of its work for the development and financing of a solar power facility in Panama.

The magic circle firm filed suit earlier this month in Manhattan Supreme Court against Qohelet Panama and affiliate Entoria Group.

The firm maintains that Qohelet never objected to its invoices and the client repeatedly claimed it would pay. But, the suit says, "defendants have failed to pay any amount for the extensive legal services that A&O provided".

According to an April 2014 engagement letter, A&O gave Qohelet a 10% discount from its standard hourly rates. Billing on the matter were New York partners Mitchell Silk, whose $975 (£750) rate was discounted to $877 (£675), and Dorina Yessios, whose $925 (£712) rate was discounted to $832 (£640), according to court documents. Four associates, with rates between $594 (£457) and $360 (£277), were also listed on the matter.

The engagement letter is signed by Vincenzo Fagiuoli and David Gutierrez del Castillo, board members of Qohelet.

The firm said it communicated with the client multiple times for payment. For instance, according to court documents, Silk wrote to Fagiuoli in October 2015: "Can you please let me know when we will be hearing back from you? The majority of the time cost on this file is well over a year old and I am under immense pressure from our finance department."

Patrick Bonner, a partner at Menz Bonner Komar & Koenigsberg, who represents the firm, did not return a message seeking comment. Fagiuoli and Gutierrez del Castillo could not be reached.

The lawsuit follows a surge in large law firms suing clients for unpaid fees in recent years. According to a review of New York City court filings carried out last year, fee disputes involving the wealthiest and largest law firms are rising compared to the past few years, when filings were fewer or initiated by smaller firms.