Pat Glass has resigned as Labour's shadow education secretary, two days after being appointed by Jeremy Corbyn.
The North West Durham MP's appointment came on Monday during a wave of resignations by Labour MPs seeking a change in leadership.
She said she was resigning "with a heavy heart" because the "situation is untenable".
On Twitter, her resignation was met with a series of angry tweets from people declaring support for Mr Corbyn.
They threatened to deselect her and called her decision "disgusting".
Ms Glass had been shadow minister for Europe and a shadow junior education minister and described the post of shadow education secretary as her "dream job".
She replaced Lucy Powell, who stepped down on Monday after saying Mr Corbyn's position as Labour Party leader had become "untenable".
Ms Glass served as a member of the education select committee during the coalition government between 2010 and 2015.