A video posted on YouTube in 2013 shows the now Shadow Chancellor describing himself as a Marxist and saying, "I've been waiting for this for a generation!"
Asked about the video today, Mr McDonnell said: "It was a joke. I also said, The bankers have done more to undermine capitalism than any of the Socialist Worker Party's activities in the last forty years.' I think it was taken as a joke, and if you listen to the tape, people fell about laughing as a result."
Before it was uncovered by The Telegraph, the video had only been viewed 60 times in the three years it has been publicly available. In 2013, Mr McDonnell was a backbencher and Labour rebel. He has been Shadow Chancellor seen he was appointed to the position by his closest political ally, Jeremy Corbyn.
In a video entitled "John McDonnell MP Speaking at communities against the cuts meeting", he says:
"We've got to demand systemic change. Look, I'm straight, I'm honest with people: I'm a Marxist.
"This is a classic crisis of the economy - a classic capitalist crisis. I've been waiting for this for a generation!
"For Christ's sake don't waste it, you know; let's use this to explain to people this system based on greed and profit does not work."
He then explains how it should be used to advocate a "system based upon planning for need and democratic control it".
The economic crash of 2008 triggered the worst recession in the UK since the 1930s, and caused hundreds of thousands of job losses.
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