Natalie Bennett’s leadership of the Green party cost the party dearly in the run-up to the 2015 general election, a leaked report into Labour’s general election defeat has found. The report, 2015: What Happened? which has yet to be published in full, obtained by Michael Savage at the Times, shows the impact that Bennett had on the Greens’ standing throughout the short campaign.

And the graph showing the Natalie Bennett Effect – it really looks like she cost the Greens: 6/6 pic.twitter.com/CNG8bwHBOy — Michael Savage (@michaelsavage) March 9, 2016

Support for the Greens declined following each of Bennett's media appearances - a mauling by Andrew Neill on the Sunday Politics, disastrous interview with LBC's Nick Ferrari, and a lacklustre showing in the seven-way debate between Bennett and the leaders of Ukip, the SNP, Plaid Cymru, Labour, the Conservative and Liberal Democrat parties.

The finding is an endorsement of Labour strategists who believed that increasing the airtime given to the Green leader, Natalie Bennett, would help Labour and hurt the Greens, but will be rued by senior Greens who, as my colleague Anoosh Chakelian revealed before the election, felt that they would be better off putting Caroline Lucas up for the televised debates. In the end, Bennett struggled in the two debates she participated in, with one preparation session having to be cancelled due to fears for the candidate's morale.

Although the report is generally scathing about Labour's performance, message and leadership at the 2015 election, its findings around Bennett and her effect on the Greens provide a crumb of comfort: with a different leader in charge of that party, things could have been worse still. For the Greens, now that Jeremy Corbyn has moved Labour into their territory, the 2015 election may well be the party's biggest missed opportunity in its history.