Labour MP Pat Glass has resigned as shadow education secretary - just two days after being appointed to the role.
The announcement comes less than 24 hours after the pro-Europe MP for North West Durham said she will not stand again.
She was promoted on Monday from shadow Europe minister to shadow education minister.
She was handed the education brief as the Labour leader struggled to find sufficient loyalists to form a team in the wake of a mass walkout and massive vote of no confidence.
Yesterday she announced she would not be standing again as an MP, and might step down as early as October.
Today she said: "It is with a heavy heart that I have today resigned. My dream job but the situation is untenable."
Mrs Glass did not attend last week's referendum count after police received four death threats.
Elected in 2010, she had not intended to serve beyond 2020.