A new poll today revealed a three point lead for Brexit, suggesting the Eurosceptic campaign has gained momentum over past fortnight.

Research by Opinium said the race was split 43 per cent to Leave and 40 per cent to Remain - the latest in a succession of surveys to show Vote Leave ahead.

The poll suggested the undecided voters - 14 per cent of today's sample - were starting to lean toward Brexit as well.

The departure of the Government machine for the final weeks of the referendum and a shift to debate about immigration appears to have driven the change.

Today's Opinium poll for the Observer revealed a three point lead for Brexit - the latest in a sequence to show the Out campaign ahead in the referendum race

Shocking official statistics revealed net migration to Britain from the EU is running at record breaking highs and the Vote Leave campaign used the figures to press hard on its offer of greater border control.

The Remain campaign today sent out Sir John Major to launch a fierce attack on Boris Johnson for leading a 'fundamentally dishonest' and 'squalid' campaign on immigration.

But Mr Johnson hit back at the former prime minister to demand Britain Stronger in Europe, championed by David Cameron, spell out a 'vision' for what continued runaway immigration would mean.

Half the people asked in today's poll, carried out for the Observer, said leaving the EU would mean Britain gaining greater control of its borders - a key win for the Out campaign.

Just 12 per cent of people think staying in the EU is the best way to get control over immigration despite Mr Cameron and others insisting quitting the trading bloc would be a terrible way of cutting the numbers coming to Britain.

Sir John today slammed Vote Leave for a campaign over immigration 'verging on the squalid'.

And speaking to the BBC the former PM condemned the 'utterly false' suggestion 88 million Turks were ready to come to Britain if the country rejects Brexit.

But in his own exchanges, Mr Johnson defended Vote Leave over immigration. He confirmed his view immigration was positive in itself but insisted it needed to controlled.

Mr Johnson said: 'The question the Remain campaign have to answer is what is their long term programme, what is their answer for the country if the numbers continue at this rate.

'At the moment, if we grow the size of a city like Newcastle every year, we will see our population rise inexorably to 70 or perhaps 80 million.

'What the Remain campaign have to say is where is our vision for this? It may be a great vision, it may be a positive thing, but where are they going to build the homes?

'What is going to happen to the green belt? How will it work for schools and hospitals and all the public services that will be affected? We are not hearing anything about how this is supposed to work.'

Boris Johnson today defended his Vote Leave campaign against charges it was making 'squalid' claims about immigration by insisting the Remain campaign spell out how it would deal with a growing population

Mr Johnson said Brexit was now crucial to meeting the Tories' manifesto promise to cut net migrations to the tens of thousands.

He told the BBC's Andrew Marr: 'I think is certainly true is that if you tell people that you can cut immigration to the tens of thousands and we all stand on that manifesto... If you then are unable legally to deliver what you have pledged because of our membership of the EU I think it is frustrating and I think people want an answer.

'What we want to hear, we're all convicted of the same crime by that token because all of us Conservatives stood on that manifesto.

'We all thought we were going to get reform of the EU as a result of the renegotiation, to adjust our immigration policy so that we would be able to cope with that, we didn't get a sausage, we didn't get anything in that renegotiation, we weren't able to change our migration.'

Vote Leave campaigner Michael Gove today said leaving the EU would allow the Government to reduce net migration to the tens of thousands, a promise made by David Cameron which he has been unable to keep.

Michael Gove made his own intervention on immigration today and said he believed Brexit would allow net migration to be brought down to the Government pledge of the tens of thousands

The Cabinet minister suggested that even if voters back Brexit in the June 23 referendum Britain will still be part of the bloc by 2020.

He told ITV's Peston on Sunday: 'We wouldn't have left the European Union by the end of this Parliament but we would in due course bring it down to tens of thousands.

'I wouldn't set a time limit for it but the ambition would be to bring it down to tens of thousands.'

Put to him that it would mean reducing both EU and non-EU immigration, Mr Gove said: 'Yes.

'I absolutely don't think (that it would damage Britain's prosperity) because at the moment uncontrolled numbers coming in here only depress wages for working people.

'It's also the case that they put a considerable strain on public services, on housing, on the National Health Service, and of course on school places.

'We grew very successfully in the 1980s and the 1990s with immigration in the tens of thousands.'

You're LYING! Sir John Major mauls Boris as a 'court jester' as he reveals his fury at 'fundamentally dishonest' Brexit campaign - but Johnson dismisses ex-PM's 'nonsense' and warns UK population will hit 80MILLION

Sir John Major today mauled Mr Johnson as a 'charming court jester' but claimed his disloyalty now would mean he would never be able to lead a united Tory party.

The ex-PM said Vote Leave was offering a 'fundamentally dishonest' case for why Britain should leave the European Union.

And he claimed: 'I'm angry at the way the British people are being misled.'

The explosive interview with the BBC's Andrew Marr was immediately followed by another with Mr Johnson - who dismissed the claims he just wanted to be PM as 'absolute nonsense'.

Sir John Major launched a savage attack on Boris Johnson during an extraordinary live interview with the BBC's Andrew Marr today

The former prime minister predicted Mr Johnson would face the same fate as Iain Duncan Smith if he seized control of the party after leading the Brexit rebellion.

In a deeply personal attack on Mr Johnson, Sir John said: 'Throughout the whole of my political life, people have regarded me as being guilty of understatement.

'I am angry at the way the British people are being misled. This is much more important than a general election - this is going to affect people, their livelihoods, their future for a very long time to come.

'If they decide to leave on the basis of inaccurate information, known to be inaccurate, then I regard that as deceitful. That is how I see their campaign... for once I am not prepared to give the benefit of the doubt.

'I think this is a deceitful campaign... they are misleading people to an extraordinary extent.'

He said: 'People are being invited to vote for a pig in a poke.'

Mr Johnson hit back in his own interview and told Marr: 'I dismiss it. We have a very short time now until the referendum and what people want to hear are the arguments.

'What we are setting out on the Leave side is an agenda for the Government to take back control on June 23 of a lot of things that really matter to the people of this country.'

Mr Johnson said it was 'absolute nonsense' he was backing Brexit for career reasons.

Asked if he believed the attacks against him were part of a plot to 'take him out', he said: 'Whether it is or not, I'm rather with John McDonnell this morning who says that there is too much of this blue on blue action and what he wants to hear is the arguments and that's where I am.'

Boris Johnson was on the BBC One set during Sir John's interview and listened to the fierce claims before dismissing them as 'nonsense'

Remain campaign field an all-woman team to take on Boris Johnson and stop his 'bluster and buffoonery' in the next big referendum TV debate

The Remain campaign is fielding an all-female team at this week's big TV debate in an attempt to shut down Boris Johnson's 'bluster and buffoonery' it was claimed today.

Tory energy secretary Amber Rudd, SNP Scottish first minister Nicola Sturgeon and Labour shadow business secretary Angela Eagle will make the case for Britain staying in the EU on Thursday night.

Boris Johnson will be joined by Tory energy minister Andrea Leadsom and Labour MP Gisela Stuart during the hour-long TV debate - meaning he will be the only man on the panel.

The Remain campaign is fielding Nicola Sturgeon, left, and Amber Rudd, right, against Boris Johnson on Thursday night in a bid to counter his 'hot air'

The Remain campaign believe their line up will be able capitalise on Mr Johnson's rhetorical style - which has provoked claims of sexism.

A senior campaign source told the Sunday Telegraph: 'The hope is that putting Boris up against such a strong line up of impressive women will fully expose Boris's bluster and buffoonery for what it really is, hot air.

'They won't let him get away with his usual antics.'

Brexit would be a 'gamble' that leaves Britain at greater risk of terror attacks warn SEVEN former police chiefs

Seven former police chiefs have urged voters to reject Brexit because it would be a gamble with security that leaves security at risk.

The officers, which include two former commissioners of the Met, said EU membership was good for security because of the access to systems such as the European Arrest Warrant.

In an open letter, the group said quitting the trading bloc would 'put us at a disadvantage in tackling terrorism and organised crime'.

Security and justice issues were cited by Home Secretary Theresa May when she announced she would be supporting the Remain campaign in February.

Among the signatories of the letter were former Met Commissioner Lord Blair (left) and Sir Hugh Orde, the former President of the Association of Chief Police Officers

And the group was backed today by former home secretary Charles Clarke and serving Home Office Minister James Brokenshire.

The seven said: 'As former Chief Officers and Policing professionals our experience has been better than most about what is required to tackle terrorism and crime and to keep the people of our country safe.

'This is why we believe that Britain will be safer inside the European Union, and that leaving Europe would make us less safe and put us at a disadvantage in tackling terrorism and organised crime.'

They added: 'The EU helps our police forces to work together, making it harder for criminals and terrorists to evade justice.

'The arrest of Hussein Osman, who plotted a bomb attack in London and tried to flee to Italy, was thanks to European Arrest Warrant.

'We do not believe that staying in Europe makes us more vulnerable, it is not credible to argue so, all the evidence is to the contrary.