28/09/2015 10:22 BST | Updated 28/09/2016 06:12 BST

Has Peter Kellner Changed His Mind on Brexit?

For as long as I can remember, Peter Kellner, a man I like, respect, admire and consider a friend for more than 30 years has been telling me that my fears over Brexit were unfounded. Peter, like myself, believes that Britain isolating itself from Europe would be a historic error of monumental proportion.

But relying on his intimate knowledge of public opinion as head of the leading polling company, YouGov, Peter Kellner has insisted again and again, on the record at public seminars and in private conversation that there would never be a majority in favour of quitting the EU.

I, on the contrary, have felt ever since David Cameron announced his referendum in January that Brexit was possible, indeed probable. It was why I wrote my book Brexit: How Britain Will Leave Europe (IB Tauris). The first edition came out in January and discussed the divide between David Cameron and Ed Miliband over holding a referendum. That question was settled in the general election and unless the referendum is called off we must assume we will hold this dangerous plebiscite.

I have since completely re-written the non-historical chapters of the book to include developments since May this year. The book's cover had been changed to a bright red instead of a pale cream and explains the new reasons since David Cameron returned to Downing Street that reinforce my Brexit arguments.

Now opinion polls are moving as it were from Peter Kellner to my side of the argument, namely that Brexit must be taken seriously. The argument that it will be like the 1975 referendum or that voters always stay with the status quo are evaporating. Simon Heffer writing in yesterday's Sunday Telegraph said the Out or Leave campaigners had already raised nearly £20 million. In 1975, the In or pro-Europe camp outspent the Out campaign 12-1. Forty years it is the anti-EU Out campaign that has all the case while the In groups rely on small groups of volunteers and small amounts of money from private donors.

Under legislation passed recently listed companies, including all major FTSE firms which back staying in the EU, cannot give money to a political campaign unless it is authorised by a special AGM. No CEO is going to risk calling a politically charged special meeting of shareholders which can be packed by UKIP activists and other anti-Europeans who buy a single share in order to secure a vote to give money to keep the UK in Europe. One recent survey said the 67% of leading UK firms wanted to stay in Europe but only 6% would campaign to that end. If big business is staying on the sidelines and not chipping in with financial help, the huge amounts of cash that have flowed and still flow from private City firms owned by Eurosceptics to Ukip or anti-European think-tanks will have more influence on the outcome than under-funded pro-EU campaigns.

The new Labour leadership is not Eurosceptic in the sense of Nigel Farage or top Tories like Boris Johnson and Sajid Javid who argue that Britain will flourish outside the EU. But Jeremy Corbyn and his closest comrades criticise the EU with its focus on austerity and free trade deals. The TUC has said its members could easily campaign for a No vote if the prime minister brings back any deal that contains language implying change in so-called Social Europe provisions.

Yet the CBI, and other employer outfits like the British Chambers of Commerce and Institute of Directors have been banging on for years that Cameron must reform, reduce or remove EU social rules like Working Time or Agency Workers Directives. Labour and the unions are not anti-European but cannot offset the relentless Eurosceptic campaign by most of the mass circulation press.

Finally, as I argued in my book, the constant criticism of the EU from politicians and journalists of right and left and the failure of all government ministers since 2010 to find a good word for Europe is working its way into public consciousness. Today The Times published a poll showing a 40-38 split in favour of voting Out or Leave.

The poll was carried out by YouGov. I expect to bump into Peter Kellner at the Labour conference or soon at one of the many discussion events on Europe at which we see each other. I look forward to his explanation of why his own polling firm now joins Survation and ICM in producing Out majorities and whether perhaps his confidence in recent times that the UK would always vote to stay in Europe was misplaced.

Denis MacShane is a former Minister of Europe and author of Brexit: How Britain Will Leave Europe (IB Tauris)