Renewing the consensus for the EU must be at the heart of the progressive agenda in Britain. Only such an agenda can provide the bulwark against the defensive nationalism and isolationism which threaten to drive us apart as Europeans, and to undermine the unity we need to help us influence the forces of global change.

But this idea of Europe is under pressure today from the forces of hyper-globalism on the one hand, and by defensive nationalism and protectionism on the other.

The hyper-globalisers – too many of whom can be found in Britain – believe in unimpeded free markets. They have no time for the welfare state. They see the EU as a bureaucratic, regional obstacle to Britain competing unencumbered in the global economy.

The protectionists see the EU as a Trojan horse for globalisation, transmitting the harsh winds of international competition to European citizens. They see enlargement and the single market – for progressives the greatest successes of the EU – as signs of the weakness of the European project and its surrender in the face of globalisation.

In Britain and elsewhere, these extremes risk undermining support for the EU. That is dangerous because in an age of global challenges and continental powers – many of whom do not share our values – the EU is vital to our ability to shape change in the interests of our citizens.

What does this mean in practice? We need economic, social and environmental policies adapted to a global age. At the heart of that agenda must be the continuing renewal of European economies, the modernisation of the European social model and strengthening the EU to shape globalisation.

Take the European single market. We have created an integrated market which removes barriers to trade and investment with the powers to enforce rules in the interests of consumers and the economy as a whole. Look at the European commission’s actions against anti-competitive practices like those of Microsoft or unreasonable mobile phone roaming charges. We need to go further, removing the remaining barriers and creating a real single market in services. And the single market needs to extend its reach, helping to shape the regulatory and competitive space beyond our borders.

The social dimension has always been at the heart of the EU. Many of the labour rights we enjoy are European in origin. In the past, some EU legislation seemed to get the balance wrong between flexibility and protection. But there has been a change in Europe over the past decade. ‘Flexicurity’, the new EU buzzword, may be ugly to British ears, but it is a social agenda that draws on the experience across Europe of modernising the welfare state, in Scandinavia in particular. More than at any time in its membership of the EU, this is a social agenda in tune with Britain’s, which we can help drive, and learn from.

On the most pressing threat to our long-term wellbeing – climate change – the EU, strongly backed by Britain, is leading the global debate. This is one of the most complex issues facing the international community and national governments. How do we show global leadership without giving other major polluters a free ride, and without exporting our industry and jobs to more polluting zones? There are no easy answers. But there can be no doubt that these issues can only be addressed – and are being addressed – at the EU level.

On trade and development, we need open European markets and open global markets. On both we need to do more. But the basic progressive argument that the EU must be open to the world is being won. We are reforming the Common Agricultural Policy to make it far less trade-distorting and have committed to make that change irreversible in the WTO Doha development round. We offer more trade opportunities to developing countries than anyone else.

On development assistance, 80 per cent of the increased global aid pledged in 2005 under the UK’s G8 Presidency – much of it intended for Africa – will come from Europe. Britain must help ensure we keep our promises.

The reality is that the EU and Britain today share a fundamentally progressive agenda. But too many on the left in Britain have abandoned the EU to its opponents. This is a grave mistake because the EU is essential to securing the values and interests of Britain in the global era. It is time for the progressive left to reclaim the case for Europe.