Britain’s exit from the European Union has relegated the country to just one of many “middle powers” in the world, former UK foreign secretary David Miliband has claimed.

In an article for the Observer published on Sunday, Miliband – who served under prime ministers Tony Blair and Gordon Brown – said the UK’s “wealth, military assets and reputation have all declined” compared to its peers.

He argued that one of the “delusions” of Brexit was to think that the UK “held all the cards” and that its destiny depended only on its own decisions rather than on the ability to “engage, incentivize, bargain with and deter others.”

The UK voted to leave the EU in  June 2016, and Brexit officially took place in January 2020. In early 2021, the country also left the European single market.

“The danger for British policymakers was exemplified by the Johnson government: wishful thinking about our power and position in a world dominated by growing global risks and muscular, transactional, adroit – sometimes predatory – nations and non-state actors, all growing in influence by the weakening of the multilateral system,” Miliband wrote.

The world is heading towards an “unhealthy disequilibrium” due to the fragmentation of global power and increasing risks, Miliband predicted, noting that Britain is “on the wrong side” of these key trends.

While the US and the West remain strong in some aspects, a host of countries are “increasingly unwilling to do as the West wants.”

“Sometimes this is because of grievances about the mismanagement of globalization; in other cases, there is hedging about Chinese or Russian power,” Miliband said.

To reverse the decline, the UK has to enter new “structures and commitments” with the EU on foreign policy, defense and security, Miliband, who now heads the International Rescue Committee (IRC) charity, suggested. The UK also needs to “understand the realities” of its power in today’s world.

“We do not have the finance of Saudi Arabia, the EU anchor of France, the regional activism and risk appetite of Turkey or the demographic strength of India or Indonesia,” he argued, describing Britain as “one among a number of ‘middle powers’ in the global system.”

London’s status on “critical” interests ranging from the economy to the climate crisis and national security will get worse “unless we get our act together,” Miliband warned.

Goldman Sachs economists earlier pointed to the high price the UK has paid for Brexit. The departure from the EU has spurred inflation and trimmed Britain’s real GDP by about 5%, compared to the performance of its economic peers, the US banking giant said in February.