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Cameron was answering a question from Corbyn in parliament during Prime Minister's Questions - known as PMQs -when he pulled out the piece of paper and proceeded to mock Corbyn for not having control of his party.
The leaked spreadsheet was published by The Times this morning.
It was allegedly put together by allies of Corbyn to divide up Labour MPs according to how loyal they are. The five groups it divides them up into are 'core,' 'core plus,' 'neutral but not hostile,' 'core negative' and 'hostile.' Cameron joked that he would include himself in the 'core' group.
Here's what he said:
"We've got a very interesting document today, we've got the spreadsheet of which Labour MP is on which side. the Honourable lady is shouting, but it says here she's neutral but not hostile. Now the chief whip on the other hand the chief whip is being a bit quiet, look there are five categories ... [interrupted by loud shouting] Mr Speaker, there are five categories, we've got the 'core support,' [more loud shouting] we've got 'core support,' I think you can include me in that lot, we've got core plus, the chief whip's being a bit quiet because she's in 'hostile.' Mr Speaker, I thought I had problems."
Corbyn tried to respond by inviting Cameron to "leave the theatre and return to reality" - but it was too late.
Labour MP John Woodcock tweeted that PMQ's was a "f****** disaster" before quickly deleting his tweet. Woodcock is listed in the leaked document as "hostile."
Twitter/JWoodcockMP
A spokesman for Corbyn told IBTimes UK and The Guardian the leader's office had no knowledge of the document:
"This doesn't come from the leader's office and we have no knowledge of it."