London Stock Exchange Group (LSE) is set to hold an extraordinary meeting before Christmas to decide the fate of its chairman and chief executive following intense pressure from an activist investor.

The Children’s Investment Fund Management (TCI), which owns more than 5% of LSE, has been calling for the shareholder meeting, which will include a motion to vote for the removal of chairman Donald Brydon and to retain chief executive Xavier Rolet until 2021.

Mr Brydon has been accused by TCI of pushing out Mr Rolet, who is currently expected to leave the firm next year.

LSE, which confirmed the meeting on Friday, is now preparing to publish a circular to shareholders providing them with details of TCI’s grievances.

According to regulatory rules, LSE must give notice to convene a meeting within 21 days and then hold the event no longer than 28 days after it has been issued.

This means that it will take place before the end of the year and before Christmas.

“London Stock Exchange Group will meet its obligations in respect of the requisition and intends to publish a circular in connection with such requisition meeting as soon as reasonably practicable,” the company said.

It comes after Christopher Hohn, investment manager of TCI, wrote to Mr Brydon, accusing him of offering poor explanations for Mr Rolet’s departure and claiming that confidentiality agreements were barring full disclosure of his plans.

“You have failed to provide shareholders with any substantive basis for the removal of the chief executive,” Mr Hohn said.

“Hiding behind confidentiality agreements denies shareholders the ability to view your actions and demonstrates the bad corporate governance over which you are presiding.”

LSE last month announced Mr Rolet would be standing down in 2018 after nearly a decade at the helm, during which time its stock market value has soared from £800 million to nearly £14 billion.

In an earlier letter to Mr Brydon from November 3, Mr Hohn argued Mr Rolet had created “enormous value” through acquisitions and “excellent operational management”.

The fund had been urging Mr Brydon to resign on his own terms, for Mr Rolet’s contract to be extended and for the group to suspend the search for his successor – warning it would otherwise trigger the extraordinary meeting.

Mr Rolet’s tenure has seen LSE seal a string of acquisitions, although it was marred by the recent failed attempt at a £21 billion merger with German rival Deutsche Borse to create a European trading powerhouse after it was blocked by the European Commission in March.

This marked the third doomed attempt at a tie-up between the two companies after previous setbacks in 2000 and 2005.