In the European elections on 10 June, the Conservatives will be competing with UKIP for the crown of the British anti-Europeans. With such an unseemly battle underway, it is sometimes difficult to remember a time when the Tories weren’t tussling on the fringes of respectable political debate.

But historically, the Conservatives were Britain’s pro-European party. Winston Churchill was an enthusiastic advocate of European integration, seeing it as a guardian against future conflict. Britain’s first application to join the EEC was submitted by Harold Macmillan’s government, believing it would strengthen Europe’s ‘struggle for freedom’. The UK finally entered the community under Ted Heath, leaving the looser European Free Trade Area at the same time. Margaret Thatcher campaigned for a Yes vote in the referendum on Britain’s continuing membership. And eleven years later, she signed the Single European Act, which meant for the first time ever that EU members could be required to abide by decisions for which they had not voted in the Council of Ministers.

Indeed, those Eurosceptics who claim that Margaret Thatcher was one of them all along should refer to the Tories’ 1983 general election manifesto. ‘The European Community is…by far our most important export market’, it states. ‘Withdrawal would be a catastrophe for this country. As many as two million jobs would be at risk. We would lose the great export advantages and the attraction to overseas investors which membership now gives us. It would be a fateful step towards isolation’. Quite so.

This contrasted with a Labour party that was by instinct far more hostile – split during the 1975 referendum, and advocating outright withdrawal in 1983. The infamous Labour manifesto of 1983 stated that the ‘next Labour government, committed to radical, socialist policies for reviving the British economy, is bound to find continued membership [of the European Community] a most serious obstacle to the fulfilment of those policies.’

So what changed? The story is not so much about a shift in attitudes to European integration per se, but of changed perceptions of what integration could achieve. In short, the Tories no longer see Europe as their friend.

The election of Margaret Thatcher in 1979 represented a key ideological turning point for the Conservatives. Until that point, both main parties remained committed to the postwar consensus – economic intervention, nationalisation, corporatism, and social standards underpinned by a generous welfare state. Thatcher’s government was determined to change all that. Furthermore, her election brought with it a significant cultural shift within the Conservative party. In place of the old-style paternalist Tory, there was now a new breed of Tory MP, more rightwing and ideological than before, less afraid of shaking things up. The Conservatives had been radicalised.

At first, the new Conservative radicals focused their energies on transforming Britain. Publicly-owned industries were privatised, new laws curbing the powers of unions were introduced, industrial subsidies were cut back and markets were liberalised. But inevitably, Europe also came within their sights. In particular, the Tories opposed the renewed moves towards integration instigated by Jacques Delors during his tenure as President of the European Commission. Under Delors, the European project was no longer simply about economic liberalisation. It had a social element too. For the Tories, this looked too much like socialism via the backdoor.

During the same period, Labour was undergoing its own transformation. Back in 1983, the party’s Europe policy was shaped by a faction which saw Europe as an enemy of socialism – as the Conservative election manifesto put it that year, the ‘Labour party wants Britain to withdraw from the Community, because it fears that Britain cannot compete inside and that it would be easier to build a socialist siege economy if we withdrew.’

But during the 1980s, that all changed. Whereas Europe had formerly been seen as an essentially capitalist project, Labour was now coming to see it as guardian against the worst extremes of Thatcherism. And this perception has been borne out. It is through Britain’s membership of the EU that workers in Britain now enjoy a 48-hour week and 20 days paid holiday a year.

For many Tories, this reversal of fortunes was impossible to stomach. Instead of being an engine of liberalisation, they now saw the EU as a grave threat to the hard-fought reforms they had delivered during the 1980s. It seemed that they had succeeded in rolling back the state in the UK, only to see it encroaching again from Brussels. What’s more, they could do little to resist this rising tide. Whereas the British constitution provides a governing party with almost uncontested power to implement its policies, Britain had no such dominance in the EU – and even less political clout.

Which brings us back to the European elections. After more than a decade of bitter in-fighting, the Conservatives are now more ideologically united than ever. The old divisions over Europe have now been largely settled in favour of the Eurosceptics. And many of them have concluded that the project of European integration is fundamentally irreconcilable with their vision of a society unshackled from state interference. Like Labour in 1983, the Thatcherite siege economy can only be built if we withdraw from Europe.

It is this which underpins Conservative thinking on the European constitution. A number of leading Conservatives, including David Heathcoat-Amory, the Tories’ representative on the European constitutional convention, have called for Britain’s relationship with Europe to be redefined. In a pamphlet for the Centre for Policy Studies, Mr Heathcoat-Amory sets out how this would be achieved following the rejection of the constitution in a referendum. ‘In practice, if a country voted no to the Constitution, the…state concerned would probably allow the others to go ahead,’ he wrote, ‘having negotiated an associate membership of some kind, from a position of considerable strength.’

For this group of Tories, the logic of further European integration is simply to collectivise and protect the kind of big government, regulation and social standards that they have been fighting against all their political careers. In its place, they want a pick’n’mix Europe, where countries like Britain would be free to opt into some elements of the project, like trade liberalisation, while rejecting others like tax harmonisation and the social chapter. This would enable us to reap the benefits of membership while simultaneously undercutting other member states through tax competition and lower employment standards.

Failing that, many Conservatives would prefer outright withdrawal to continued membership. John Bercow, the shadow international development secretary, has advocated four possible alternatives to EU membership – membership of the European Economic Area, the ‘Swiss option’, membership of Nafta, and even no agreement at all. On Nafta, he argues that its ‘culture, distinctively Thatcherite, fits more neatly with Britain’s experience than the corporatist dirigisme of the EU’ and singles out the ‘combination of low taxes, restrained public spending and labour flexibility” as particular advantages to the Nafta model. Similarly, Andrew Rosindell, appointed vice chairman of the Conservative party by Michael Howard, has asserted that ‘Europe is going in entirely the wrong direction and I think it is time for Britain to get off this train, which is hurtling into the buffers.’

These are the issues that Labour voters need to keep in mind on 10 June. Many Labour voters will feel sympathetic towards Michael Howard’s call for a more flexible Europe. Some may even find themselves voting for UKIP, believing that policy should be decided in London not Brussels. But to do so would be a grave error. The movement to loosen Britain’s ties with Europe is fundamentally rightwing in character. For the Tories, the real issue is not whether a decision on the minimum wage or on working times should be taken in Brussels, but whether it should be taken at all. All those who believe that the state has the duty to protect its citizens must do all they can to resist Tory anti-Europeanism.