Britain leaving the EU could signal a new shift away from multilateralism as leaders around the world increasingly talk about pulling up the drawbridge against globalisation and retreating into isolationism. This would be a mistake.

The EU is enfeebled because its members cannot reach consensus on critical issues, for example, processing refugees. The EU remains a project of states despite its attempts at designing supranational institutions. If Britain votes to leave the EU on 23 June, it will turn its back on the most ambitious attempt at multilateralism in the 20th century. It will also abandon the opportunity to make the EU function better. 

Martin Wolf has observed that multilateral institutions are underperforming across the board. His frustration is not so much with the current international architecture as with the lack of political will to make existing institutions work. In his words, 'systems of cooperation among states are ultimately dependent on what states are willing to give them, both the legitimacy and the power'. 

International pressure has been building against Brexit, and not just from other EU countries. The G7 and G20 have made statements about the potential ramifications of Brexit. The G7 concluded last month that 'a UK exit from the EU would reverse the trend towards greater global trade and investment, and the jobs they create, and is a further serious risk to growth'. This follows the G20 Finance Ministers and Central Bankers' communiqué in February listing 'the shock of a potential UK exit from the European Union' as one of the downside risks and vulnerabilities for the global economy. 

Those campaigning for Brexit believe the UK will have a menu of other multilateral options outside of the EU. Stewart Patrick from the Council on Foreign Relations has written about the emergence of 'multilateralism à la carte' whereby states choose coalitions and approach issues case by case, rather than using the international organisations themselves to hammer out collective agreements. 

However, for Britain, there is a lot of evidence that its multilateral menu is more extensive inside the EU. David Skilling has pointed out that the EU is 'a valuable asset for European countries, enabling them to negotiate FTAs that they would not get bilaterally'. Robin Niblett has also made a compelling case for why 'working through EU institutions, despite their flaws, and with the UK's European neighbours offers the best prospects of managing the changing global context'. 

The UK will not be able to fall back on its bilateral relations as a substitute for multilateralism – either with its post-war ally, the US, or its new favourite economic partner, China. Both the US and China have made clear that they would prefer the UK to stay in the EU.

President Obama has been unequivocal about US opposition to Brexit, saying 'the UK is at its best when it's helping to lead a strong European Union. It leverages UK power to be part of the EU'. Hillary Clinton agrees. As usual, it is difficult to say what Donald Trump's position would be. 

Even China does not like the possibility of Britain leaving the EU. President Xi said in his state visit to the UK last year, 'Britain, as an important member of the EU, can play an even more positive and constructive role in promoting the deepening development of China-EU ties'. 

The challenges that the UK faces in the 21st century are global. Like everyone else, Britons will need to manage unprecedented flows of capital, goods, services and people. The UK will have to rely on international cooperation. It will lose out if it does not play a constructive role in multilateral institutions, including the EU.

Photo courtesy of Flickr user Number 10.