Simon Danczuk has announced his resignation from the Labour party, who he claims have "lost touch.. with reality in 21st Century Britain".
Mr Danczuk was told last Tuesday that he would not be allowed to stand as the Labour candidate in Rochdale, where he was the sitting MP after being suspended over a sex-text scandal with a young constituent.
In a scathing resignation letter posted to his Twitter page on Monday - and photographed alongside a Labour Party membership card cut in two - he wrote: "The way in which the party are treating the Parliamentary seat of Rochdale as a 'safe seat'... which they can parachute a Corbyn supporting candidate is deplorable".
Mr Danczuk has held the Rochdale seat since winning it from the Liberal Democrats in 2010.
He was suspended from the party in December 2015 after sending explicit text messages to a 17-year-old girl, but continued to represent the seat as an independent.
The long-standing critic of leader Jeremy Corbyn claimed the party was "no longer the positive political movement" that he joined almost 30 years ago.
He wrote, under Mr Corbyn's leadership, the party has become "more interested in serving its own ends rather than hard working people for whom the party was established."
In the letter, addressed to Labour's general secretary Iain McNicol, he added: "With frontbench spokespeople, such as John McDonnell, continually obsessing about Karl Marx, the benefits of communism and celebrating the reign of Joseph Stalin [the party] has totally lost touch with its social democratic values.
"I hope that one day... the Labour party will see sense and return to a more moderate form of social democracy", he concluded.