Wearside MP Sharon Hodgson has resigned from her shadow ministerial role today.
The MP for Washington and Sunderland West has written to Labour leader Jeremy Corbyn explaining her decision to resign from the position of shadow minister for children and families.
In her letter, Mrs Hodgson says she has not taken the decision "lightly".
The full text of the letter read: "It is with great regret and sadness that I write to you today to tender my resignation as Shadow Minister for Children and Families.
"I want to make it clear that this decision has not been taken lightly.
"Whilst I did not support you during the leadership contest last summer, your mandate was undeniable, and so, unlike others, I welcomed the opportunity to serve in your front bench team as Shadow Minister for Children and Families.
"I was pleased to work on the many policies that we both have common agreement on, including support for children with special educational needs and disabilities and ensuring that every child, no matter their circumstance or needs, has the best start in life.
"It has now become apparent that you cannot command the support of the wider PLP (Parliamentary Labour Party".
"Over the last two days we have seen resignation after resignation of from talented and experienced shadow cabinet members and shadow ministers and this morning our deputy leader asked you to consider your position as did other shadow cabinet colleagues who have resigned also.
"Now more than ever we need an effective and united opposition as we are entering uncharted territory, facing a Tory Government that will be under even more right-wing leadership.
"Labour needs to be involved at the highest levels of the EU exit negotiations to obtain the best deal possible for our people and our country, and I am not confident that you can give us that leadership."
Mrs Hodgson added: "This is even more concerning now that the extent of your ambivalence and lacklustre campaigning to remain in the EU has come to light.
"Therefore I do not believe you are the right person to lead these negotiations on Labour's behalf in the coming weeks and months ahead, and believe you have let down the many people who elected you in such large numbers to be our leader last summer.
"For this very same reason, I also believe that you will not be able to command the necessary support of the wider electorate during an expected snap general election later in the year.
"I fear your leadership could force Labour into fightng for its very existence rather than campaigning to form the next Government. I am convinced that this will leave the people that we both came into politics to help and serve in a far worse position, abandoned for a generation.
"I have always believed, and always will, that a Labour Government is the best way forward for my constituents, my region and our country; rather than being a party of permanent opposition.
"Sadly and respectfully, I do not think you can lead us into Government and therefore believe you should do the honourable, decent and selfless thing - personal qualities that I know you possess - and step aside to ensure Labour can be the united and effective party that I know we have been and can be again.
"I want you to be remembered as the Labour leader who invigorated our membership, not the Labour leader who irreparably broke the party that we both hold so dear."