Jeremy Corbyn waves to supporters after delivering a speech following the pro-Brexit result of the U.K.'s EU referendum vote in June 2016 | Odd Andersen/AFP via Getty Images Jeremy Corbyn’s team reluctant to support Remain: leaked emails Emails show bickering between Labour leader’s team and party’s official pro-EU campaign group.

U.K. Labour leader Jeremy Corbyn's team has been accused of failing to support the campaign for Britain to remain in the EU, with leaked emails showing Corbyn's head of strategy had to be forced to include pro-EU lines in speeches.

According to emails leaked to Buzzfeed, Seumas Milne, an influential member of the Corbyn team, was taken to task by Labour In For Britain, the party’s official pro-Europe campaign, for failing to include positive messages about the EU in a draft speech in May.

"There is no EU content in there. We agreed to have Europe content in this," the unnamed Labour In For Britain member wrote to Milne, a former journalist. An email exchange shows Milne eventually agreed to include two paragraphs about the EU in the speech, but refused to send these lines out to the press.

Another email exchange from December 2015 shows the first version of a speech to be given by Corbyn in Brussels attacked the EU, saying it "isn't delivering for people in crucial ways." Milne later agreed to present the bloc in a more positive light, after being prompted by a member of Labour In For Britain.

Corbyn's challenger for the Labour leadership, Owen Smith, has accused his rival of voting for Britain to leave the EU.

“I’m not even sure that Jeremy did vote ‘in’ in the EU referendum,” Smith said at a hustings in Glasgow. “One reason why Jeremy can be so complacent and passive about this is that he’s happy about the result.”

Corbyn denied the accusation, telling Smith to behave like a “grown-up.”