New Delhi: The army has sacked a married lieutenant colonel for his "unbecoming relationship" with a fellow officer's daughter, defence ministry sources have revealed.

An official said the decision was taken at the highest level, and "and after much deliberation", because of the sensitivity of the case. "An inquiry found the officer's conduct unbecoming of a senior officer," he said.

Sources said the sacked officer's wife had recently appealed unsuccessfully to defence minister Nirmala Sitharaman to reinstate her husband. The officer can now approach the civil courts to challenge his dismissal.

Senior officers at army headquarters declined to talk about the dismissal. "The armed forces demand high standards of morality," one official said.

There have been past instances of officers being fired for extra-marital relationships with fellow officers' wives.

However, the Supreme Court had in 2015 ordered the reinstatement of a navy commander who had been sacked for his alleged relationship with a fellow officer's wife, ruling that the alleged "adulterous relationship" appeared consensual.

A board of inquiry had held the commander guilty of exchanging explicit sexual messages and images, including his nude photographs, with the wife of another naval officer.