French EDF Group's designee on Constellation Energy Group's board of directors resigned Monday in the latest move between the two companies, whose relationship has been strained over a proposed third nuclear reactor at Calvert Cliffs.

The resignation of Daniel Camus, EDF's chief financial officer who spearheaded the company's involvement with Constellation, is effective Thursday, according to documents filed Monday with the Securities and Exchange Commission. No reason was given for his departure.

EDF has nominated Samuel Minzberg, a partner in the Montreal law firm of Davies Ward Phillips & Vineberg LLP, to replace Camus. Minzberg specializes in corporate and commercial law with an emphasis on mergers and acquisitions, and corporate reorganizations, according to a biography on the firm's website.

The two companies have been trying to develop nuclear projects in the U.S., most prominently at Calvert Cliffs in Southern Maryland. But the plans were thrown into doubt earlier this month when Constellation pulled out of negotiations with Obama administration officials over a federal loan guarantee deemed crucial to the Calvert Cliffs project.

Constellation offered last week to sell its half-stake in the project to EDF, after the French company offered to buy out the Baltimore company's interest in their nuclear development venture and move the Calvert Cliffs project forward – provided that Constellation not force EDF into another deal.

EDF said it is reviewing Constellation's buyout proposal.

EDF and Constellation are at odds over a provision that gives Constellation the option to sell some of its nonnuclear power plants to EDF for up to $2 billion. That so-called put option, which expires Dec. 31, was part of an EDF agreement that bailed out Constellation from a financial crisis two years ago.

EDF gained one seat on Constellation's board when that deal closed. Constellation is required to elect an individual nominated by EDF under an agreement between the two companies. EDF is Constellation's largest shareholder.

Minzberg is expected to be elected to the board at the Oct. 22 regular board meeting.