Writing to Labour leader Jeremy Corbyn, McKinnell said: "I have found it increasingly difficult not to be able to speak up in the commons about matters that are of huge importance to my constituents."
Last week Corbyn embarked on his front bench shake-up, which some critics labelled a "revenge" reshuffle.
However, Corbyn this morning defended his reshuffle against claims that he abandoned his so-called new politics and instead returned to the old politics of splits and resignations.
Yet, while McKinnel said she had huge respect for Corbyn personally, she added that she had concerns over "the direction and internal conflict within the Labour party", which she fears is taking it down an increasingly negative path.
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