Cameron's calls for flexibility risk undermining one of Thatcher's greatest legacies: the single market

The PM's clumsy approach to diplomacy, such as his veto over the EU treaty changes in December 2011, is isolating the UK and diminishing its influence in Brussels

Poor David Cameron has, once again, had his plans to explain his Europe policy derailed by events. In January, a terrorist attack on an industrial facility in Algeria led to a delay in his referendum announcement. Now, the death and funeral of Mrs Thatcher obliged him to cut short his meetings with Spain's Prime Minister, and to cancel his meeting with President Hollande of France, though he still managed to take his family to Schloss Meseburg to spend time with the Merkels.

Cameron is trying desperately to garner support in other EU capitals for the ideas proposed in his speech on the EU back in January. While it might have been wiser to consult his European counterparts prior to his speech, the answer would undoubtedly have been the same - other EU countries are simply not willing to let the UK pick and choose which rules it wants to obey while maintaining full access to the single market.

One reason for this is that granting opt-outs would allow the UK to undercut the rest of Europe, by lowering standards in areas like social and employment or environmental legislation. More fundamentally, however, it would set a precedent that could ultimately lead to the unravelling of the single market. If the UK was allowed to decide which rules it wanted to obey, there would be nothing to stop other countries from doing the same. France could opt of rules on state aid which prevent unfair competition, Germany could flout laws cutting carbon emissions to favour its automotive industry, Hungary could interfere with impunity in the independence of the judiciary. The whole system which underpins free trade in Europe would collapse. This is why there is no appetite in the rest of the EU for Cameron's Europe a la carte. The common market relies on a common set of rules, agreed on and abided by across all Member States. This is the fundamental compromise on which it was founded; while no country gets everything it wants, the overall benefits of cooperation hugely outweigh the costs.

As the country reflects on the death of Margaret Thatcher, it is worth remembering that the former Prime Minister and her Commissioner Lord Cockfield were among the pioneers in the creation of Europe's single market, which over the past twenty years has permitted an unprecedented rise in free trade across our continent. It would be rather ironic if another Conservative Prime Minister were the author of its demise. And, though by no means a Europhile, Thatcher fully recognised the importance of the EU and Britain's place in it. She once stated: “Britain does not dream of some cosy, isolated existence on the fringes of the European Community. Our destiny is in Europe.”

Crucially, Margaret Thatcher knew what she wanted and how to get it, as shown by her success in securing the British rebate on the EU budget. Her fearsome reputation and unwillingness to bend earned her the nickname 'The Iron Lady'. Cameron's propensity for u-turns and vague statements on flexibility risks earning him the soubriquet 'The Plasticine Man'.

The Prime Minister's central problem is that he is unable to square the irrational demands of the eurosceptic wing of his party with the everyday reality of Britain's relations with our EU partners. This is deeply damaging to Britain's national interest. Perhaps the prime current example is the Conservative Party's desire to opt out of crucial EU police and judicial cooperation measures. Britain's self styled 'party of law 'n order' is now being warned by our leading crime fighters that our citizens will be less secure if the Home Secretary gets her way.

More widely, Cameron's clumsy approach to diplomacy, such as his unnecessary veto over the EU treaty changes in December 2011, is isolating the UK and diminishing its influence in Brussels.

If the PM were more serious about Britain's national interests and less preoccupied with the internal divisions in his party, he would be focusing his efforts on promoting free trade and competitiveness through EU-wide reform. Many other member states share Britain's desire to improve Europe's global competitiveness by cutting red tape and expanding the single market into the services, energy and the digital sectors. Likewise, there is substantial support for promoting free trade with the rest of the world, including the recent progress towards a game-changing new trade deal with the US and a free trade agreement with India - both of which would boost growth and jobs in the UK. With Europe's economy facing global decline and a pressing need to kick-start economic growth, there has never been a better time for the UK to push for radical reform of EU policies.

The Liberal Democrats have always worked to reform the EU in order to make it more effective, efficient and legitimate. Recently, Liberal Democrat MEPs have led the way on reducing the burden of EU regulation on small businesses, reforming the EU's Common Fisheries Policy and clamping down on tax evasion. We want the EU to do more in areas where it adds value, such as enabling economic growth, fighting organised crime and combating climate change, and less in areas where it doesn't. This requires building alliances and forging compromises, not threatening to throw the rattle out of the pram.

Sir Graham Watson is a Liberal Democrat MEP and President of the Alliance of Liberals and Democrats for Europe Party