In a Facebook post on Monday, Ms Birtukan cited health as her reason to leave her post. Parliament still has to accept the resignation.

She is a former judge and political prisoner, and her appointment more than four years ago was seen as part of reform measures introduced by a new government.

In 2018, Prime Minister Abiy Ahmed took office pledging to end decades of authoritarian rule.

When he recommended Ms Birtukan to the all-important post of chairperson of the electoral board, he described her as someone who would "never surrender, even to the government".

She presided over the board that was at the centre of controversy over the postponement, due to Covid, of general elections that should have been held in May 2020. 

The delay of the elections - seen by political elites in the country’s Tigray region as a pretext for Prime Minister Abiy to stay in power unconstitutionally - contributed to the breaking out of a civil war in which more than half a million people are estimated to have been killed. 

The election was held a year later across the country except in war-hit Tigray.

In a recent interview with the BBC, Ms Birtukan said that currently the environment in Tigray was not conducive to the holding of elections there due to the continuing humanitarian crisis. 

Earlier this year another senior figure, Meaza Ashenafi, resigned. Her appointment in 2018 as the head of the country’s Supreme Court had also seen as a sign of Ethiopia’s strides towards democracy.