The FTSE-100 group said Cowgill, executive chairman since 2004, will step down from his role with immediate effect.

It said that following a governance review it had decided to accelerate the separation of the roles of chair and chief executive.

Helen Ashton, a JD non-executive director and chair of its audit and risk committee, will become non-executive chair, while Kath Smith, JD's senior non-executive director and a former Adidas, Reebok and The North Face executive, will become interim CEO.

JD said the process to recruit a CEO remains ongoing and a process will commence to recruit a new non-executive chair.

The company had said last year it would split Cowgill's role as executive chairman and recruit a CEO in 2022.

"As our business has become bigger and more complex, what is clear is that our internal infrastructure, governance and controls have not developed at the same pace," said Ashton.

"As we capitalise on the great opportunities ahead of us, the board is committed to ensuring that we have the highest standards of corporate governance and controls appropriate to a FTSE-100 company to support future growth."

Analysts were taken aback at the abruptness of Cowgill's exit.

"We anticipated a more gradual process: an internal appointment for the CEO role and Cowgill to remain as chair to oversee the transition for a couple of years," said Shore Capital analyst Eleonora Dani.

Last week JD upgraded its profit outlook.

Shares in JD closed down 6.1%.

(Reporting by Sinchita Mitra in Bengaluru and James Davey in London; Editing by Shailesh Kuber, Alexandra Hudson)