The blame game for losing the EU referendum has begun as senior figures in the Remain campaign accused Downing Street of “arrogance and timidity”, while David Cameron’s allies pointed the finger at Jeremy Corbyn's failure to convince many traditional Labour supporters to vote In.

An inquest into the Remain camp’s catastrophic defeat is underway amid bitter recriminations. Insiders in the cross-party Britain Stronger in Europe (BSE) campaign have told The Independent that Number 10 made a series of disastrous mistakes, and that Jeremy Corbyn’s office neutered their efforts by preventing Labour playing a full part.

The shock of defeat for the Remain camp was all the greater because on the morning of Thursday’s referendum it believed it would win by between five and eight points. That was the forecast made by its pollster Andrew Cooper and Jim Messina, the American former strategist to Barack Obama who helped Cameron win his general election victory last year.

“It was extraordinary that they failed to pick up the depth of anti-EU sentiment,” said one Remain source. “We knew we had problems in the North East, Yorkshire and Wales, but we had no idea of the scale of it. With hindsight, the warning signs were there, but we didn’t act on them.” The failure of intelligence led to a reluctance to speak about immigration, which became a crucial vote-winner for the rival Leave camp. Remain’s internal polling showed that Cameron’s plan to delay EU migrants full access to benefits for four years was popular – but that most voters did not know about it.

Early in the battle, Cameron’s operation considered running its own campaign. Will Straw, BSE’s director, worked hard to head off the threat in order to maintain a cross-party effort. But the price was that Downing Street often called the shots.

Remain sources claimed that Cameron and George Osborne were “scared off” by the hostile reaction to the Chancellor’s warning that Brexit would every household losing £4,300 a year. Remain was ordered not to repeat it -- in a sharp contrast with the Leave camp, which stuck rigidly to its equally controversial claim that Brexit would save taxpayers £350m a week.

Brexit - Some Leave voters are regretting their vote

“Number 10 was guilty of timidity and arrogance,” said one Remain source. “It wanted to repeat the campaign on the economy in the [2014] Scottish referendum and the general election. Its simple message worked then but the EU referendum was more complicated and needed a more nuanced one.”

Remain leaders believe they made a big mistake by not explaining to voters the benefits of the EU single market, which should have been integral to a campaign based on the economy. They say that the public's vague sense that the EU was good for the economy was trumped by their anxiety about immigration.

Number 10 also stopped Remain from launching hard-hitting attacks on Boris Johnson and Michael Gove, the leaders of the Leave effort, another insider claimed. Instead, it orchestrated its own criticism through Sir John Major, the former Prime Minister.

6 ways Britain leaving the EU will affect you Show all 6 1 /6 6 ways Britain leaving the EU will affect you 6 ways Britain leaving the EU will affect you More expensive foreign holidays The first practical effect of a vote to Leave is that the pound will be worth less abroad, meaning foreign holidays will cost us more nito100 6 ways Britain leaving the EU will affect you No immediate change in immigration status The Prime Minister will have to address other immediate concerns. He is likely to reassure nationals of other EU countries living in the UK that their status is unchanged. That is what the Leave campaign has said, so, even after the Brexit negotiations are complete, those who are already in the UK would be allowed to stay Getty 6 ways Britain leaving the EU will affect you Higher inflation A lower pound means that imports would become more expensive. This is likely to mean the return of inflation – a phenomenon with which many of us are unfamiliar because prices have been stable for so long, rising at no more than about 2 per cent a year. The effect may probably not be particularly noticeable in the first few months. At first price rises would be confined to imported goods – food and clothes being the most obvious – but inflation has a tendency to spread and to gain its own momentum AFP/Getty Images 6 ways Britain leaving the EU will affect you Interest rates might rise The trouble with inflation is that the Bank of England has a legal obligation to keep it as close to 2 per cent a year as possible. If a fall in the pound threatens to push prices up faster than this, the Bank will raise interest rates. This acts against inflation in three ways. First, it makes the pound more attractive, because deposits in pounds will earn higher interest. Second, it reduces demand by putting up the cost of borrowing, and especially by taking larger mortgage payments out of the economy. Third, it makes it more expensive for businesses to borrow to expand output Getty 6 ways Britain leaving the EU will affect you Did somebody say recession? Mr Carney, the Treasury and a range of international economists have warned about this. Many Leave voters appear not to have believed them, or to think that they are exaggerating small, long-term effects. But there is no doubt that the Leave vote is a negative shock to the economy. This is because it changes expectations about the economy’s future performance. Even though Britain is not actually be leaving the EU for at least two years, companies and investors will start to move money out of Britain, or to scale back plans for expansion, because they are less confident about what would happen after 2018 AFP/Getty Images 6 ways Britain leaving the EU will affect you And we wouldn’t even get our money back All this will be happening while the Prime Minister, whoever he or she is, is negotiating the terms of our future access to the EU single market. In the meantime, our trade with the EU would be unaffected, except that companies elsewhere in the EU may be less interested in buying from us or selling to us, expecting tariff barriers to go up in two years’ time. Whoever the Chancellor is, he or she may feel the need to bring in a new Budget Getty Images

Remain leaders claim that Cameron’s team was reluctant to allow Labour voices to take centre stage. Although a “Labour week” was earmarked two weeks before the referendum and there were speeches by Gordon Brown and Corbyn, on day three Osborne presented his much-criticised “Brexit Budget” and the following day Cameron was the main player.

However, In campaigners are equally critical of the Labour leadership. They claimed Corbyn’s office refused to allow Labour Party Headquarters to work closely with Remain; banned Labour politicians using material and pro-EU arguments drawn up by the campaign and stopped Labour figures appearing at events organised by Remain platform even though they would have secured prominent media coverage. When Remain allocated Corbyn space in its day-to-day battle plan, he did not deliver – for example, by not making a speech as planned and instead issuing a bland written statement that secured little media attention.

“Team Corbyn took the view that we [at Remain] were all Tories,” said a Labour figure involved in Remain. “It was clear that Corbyn’s heart wasn’t in it. In my view, he won’t be upset at the referendum result.” Corbyn aides deny that he made only a half-hearted effort and insist that he wanted Britain to remain in the EU.

Cameron allies dismissed the charge of “timidity and arrogance.” One said: “Remain was very much a cross-party effort involving Conservative, Labour and Liberal Democrat people who worked well together. It was based on the research we had, not Number 10's view. Our economic message was right but it did not cut through because most newspapers filtered it out. It wasn’t timid; we were pilloried for running Project Fear. It’s true that we didn’t want personal attacks because that would have just fuelled headlines about ‘Tory wars’.”