YouGov has denied claims it spiked a poll in the run-up to the General Election 2017 because it was "too positive about Labour".

Chris Curtis, former member of staff at YouGov, alleged on Twitter on Wednesday that he was banned from publishing a poll following a debate in Cambridge Jeremy Corbyn took part in, in which results were "stark" and showed Labour had won "by a mile" and one in four Tory voters thought Corbyn was best. 

But YouGov has hit back and said this is "plainly wrong".

Curtis said: "We did a fantastic debate poll in the hours following the debate that Corbyn took part in. The results were stark - Corbyn won by a country mile, and one in four Tory voters thought he was best

"Despite having written the story and designed the charts, we were banned from releasing the story because it was too positive about Labour."

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YouGov bosses said when the poll was reviewed by the team, it was clear the sample of people who watched the debate "significantly over-represented Labour voters from the previous election". 

In a statement, YouGov said: "Chris Curtis’s allegation that we supressed a poll because the results were 'too positive about Labour' is incorrect. There was a poll run by Chris following the debate in Cambridge on May 31, 2017.

"When reviewed by others in the YouGov political team, it was clear that the sample of people who watched the debate significantly over-represented Labour voters from the previous election.

"We take our responsibilities as a research organisation seriously and we could not have published a poll from a skewed sample that favoured any party. No serious polling organisation would have published this.

"The idea that YouGov would suppress a poll that was 'too positive about Labour' is plainly wrong – as evidenced by the fact that in the 2017 election YouGov published an MRP model showing Labour doing significantly better compared to most other polling organisations."

Curtis also claimed now education secretary Nadhim Zahawi threatened the job of YouGov CEO Stefan Shakespeare over the company's prediction of a hung parliament.

YouGov or Zahawi have not yet responded to this claim. 

UPDATE: Curtis has since apologised to YouGov for the allegation. 

He said on Twitter: "In a purely personal capacity, yesterday I tweeted about my time at YouGov, stating that YouGov banned us from publicising a 2017 poll which Jeremy Corbyn because it was too positive about Labour.

"While this was not my view at the time, I now accept YouGov's position that in fact the results were pulled because of concerns other members of the team had about the methodology.

"I also believe then, as I do now, that the methodology was acceptable and the survey was conducted to the highest standard. Just like YouGov, I would not be willing to put my name to any research that did not meet these standards.

"Also, as I later sought to make clear I did not intend to allege that Nadhim Zahawi played any role in this decision. I am happy to clarify the position and apologise to YouGov for any confusion caused."