Labour's "uncritical" stance of the EU helped fuel the UK's decision to vote to Leave the political and economic union, one of the party's top individual donors has claimed.

John Mills, who funded and campaigned for the Leave side ahead of the historic 23 June referendum, said the pro-Remain party should have adopted a more nuanced approach to help drum-up support for its position.

"It did seem to me that the Labour Party called this referendum wrongly," Mills told IBTimes UK.

"There were 9.3 million people who voted Labour in the general election in 2015, about 3.5 million (37%) voted to Leave."

"If the Labour Party had a more critical but constructive policy towards the EU – which didn't necessarily advocate people voting for Out – it would have resonated better with most Labour voters."

Mills, who founded Labour Leave and quit as deputy chair of the Vote Leave group during the campaign, also thought Jeremy Corbyn put on a "lacklustre" performance during the referendum – a charge anti-Corbyn activists have levelled against the left-winger during the party's latest leadership election.

"I think Jeremy Corbyn has a long record of Euroscepticism. This was inevitably reflected in his lacklustre enthusiasm for promoting the Remain cause," Mills said.

"I can understand why he got into a situation, where he thought he really had no alternative but to support Remain."

Mills failed to reveal who he is backing in the Labour leadership campaign, which was triggered on the back of the Leave result. He did, however, brand Owen Smith's pledge to hold a second referendum to "ratify" a Brexit as a "really bad proposal".

"Firstly, it's very undemocratic, but secondly how on earth is this going to work? We are now committed to negotiating ourselves out of the EU. If there's a referendum at the end of the day on whether these terms are satisfactory, what happens if they're turned down?

"Rightly or wrongly, the decision has been taken and we ought to stick to it and see it through. Calling for second referendum is just muddying the waters and is in great danger of leaving us in limbo with no viable policy in place at all."

As for triggering Article 50 of the Lisbon Treaty, the official mechanism to split from the EU, Mills wants the government to make the move at the end of 2016 or in early 2017 to fit in two years' worth of negotiations before the next general election, which is scheduled for 2020 under the Fixed-term Parliaments Act.

"The sooner we can get through all of this process and come out the other end, the better," he said. And on the issue of EU nationals in the UK, the JML founder backed Labour MP and Vote Leave campaigner Gisela Stuart in urging the government to commit to protecting their rights.

"I think we should give those assurances even if it's done on a retrospective basis," Mills added.

'Labour Future'

He is now planning to launch a new pressure group called Labour Future in a bid to help the party reconnect with lost working-class/blue collar voters. The entrepreneur claimed Labour have failed to effectively attack the Conservatives over the "unbalanced" nature of the UK economy.

"It seems to me that there is a very obvious line of attack there that the Labour Party hasn't undertaken at all. I think that's strange," he argued.

Mills added: "The EU issue is an important issue, but I think it's a minor one compared to what's happened on the economy. Over 10 years people haven't had wage increases, there's been more and more insecurity, there's been more inequality and the economy's grown a bit."