In his annual Guildhall speech on foreign policy, the Prime Minister accused opposition politicians of offering a “corrosive, inward-looking attitude” on international affairs.

Taking aim at those who advocate leaving the European Convention on Human Rights or Nato, he said they offered “grievance rather than hope” and “a declinist vision of a lesser Britain”.

Prime Minister Sir Keir Starmer speaking during the annual Lady Mayor’s Banquet at the GuildhallSir Keir addressed the UK’s international positioning during the speech (Stefan Rousseau/PA)

Sir Keir said: “Moreover, it is a fatal misreading of the moment, ducking the fundamental challenge posed by a chaotic world – a world which is more dangerous and unstable than at any point for a generation, where international events reach directly into our lives, whether we like it or not.”

He added: “In these times, we deliver for Britain by looking outward with renewed purpose and pride, not by shrinking back. In these times, internationalism is patriotism.”

Since coming to power last year, Sir Keir has been active on the world stage, trumpeting deals with the US, India and the EU and leading the “coalition of the willing” in support of Ukraine.

(left to right) Prime Minister Sir Keir Starmer, France’s President Emmanuel Macron and German Chancellor Friedrich Merz during a trilateral meeting at the G20 summit in Johannesburg, South AfricaSir Keir, left, pictured with French President Emmanuel Macron, centre, and Germany’s Chancellor Friedrich Merz at the G20 last month, has been criticised for the amount of time he has spent on the international stage (PA)

But he has also faced criticism from his opponents, who accuse him of spending too much time out of the country attending international summits rather than focusing on domestic issues.

Speaking in the City of London on Monday evening, the Prime Minister offered a defence of his approach, describing it as “the biggest shift in British foreign policy since Brexit” and “a decisive move to face outward again”.

While saying he would “always respect” the Brexit vote as a “fair, democratic expression”, he said the way the UK’s departure from the EU had been “sold and delivered” was “simply wrong”.

Sir Keir Starmer and Lady Mayor of London Dame Susan Langley (left) in the banquet procession during the annual Lady Mayor’s Banquet at the Guildhall in central LondonSir Keir Starmer and Lady Mayor of London Dame Susan Langley (left) in the banquet procession during the annual Lady Mayor’s Banquet at the Guildhall in central London (Stefan Rousseau/PA)

He said: “Wild promises were made to the British people and not fulfilled. We are still dealing with the consequences today.”

And he defended his Government’s thaw in relations with China, rejecting a “binary choice” between the “golden age” of engagement under David Cameron and the “ice age” under more recent Conservative prime ministers.

Arguing that failing to engage with China was “a dereliction of duty”, he said: “This is not a question of balancing economic and security considerations. We don’t trade off security in one area, for a bit more economic access somewhere else.

Prime Minister Sir Keir Starmer (centre) with Lady Mayor of London Dame Susan Langley (centre left) with Mayoral Consort Gary Langley (centre right) attending the annual Lady Mayor’s BanquetPrime Minister Sir Keir Starmer (centre) with Lady Mayor of London Dame Susan Langley (centre left) with Mayoral Consort Gary Langley (centre right) attending the annual Lady Mayor’s Banquet (Stefan Rousseau/PA)

“Protecting our security is non-negotiable – our first duty. But by taking tough steps to keep us secure, we enable ourselves to co-operate in other areas.”

Earlier in the year, the collapse of the trial of two alleged Chinese spies triggered a row over whether the Government had deliberately undermined the case to preserve relations with China – a claim ministers firmly rejected.

In his speech on Monday, Sir Keir said China posed “national security threats to the UK”.

Sir Keir (centre) with Speaker of the House of Commons Sir Lindsay Hoyle (right) during the banquetSir Keir (centre) with Speaker of the House of Commons Sir Lindsay Hoyle (right) during the banquet (Stefan Rousseau/PA)

But he also described the country as “a defining force in technology, trade and global governance” and said Britain needed a China policy “that recognises this reality”.

He said: “We’re absolutely clear that when it comes, for example, to defence, AI or our critical national infrastructure, we will always protect our security and our economic interests.

“But we’re also clear that in areas where there is no significant risk, we are going to give businesses the confidence, clarity and support they need to win these opportunities, with all the necessary mitigations in place.”

Commenting on the speech, Conservative shadow foreign secretary Dame Priti Patel said Sir Keir had become “Beijing’s useful idiot in Britain”.

She said: “From China’s continued flouting of economic rules to transnational repression of Hong Kongers in Britain, Stamer’s ‘reset’ with Beijing is a naive one-way street, which puts Britain at risk while Beijing gets everything it wants.

“Starmer continues to kowtow to China and is captivated by half-baked promises of trade. Coming just days after the latest Chinese plot to interfere in our democracy was exposed, his love letter to the Chinese Communist Party is a desperate ploy to generate economic growth following his Budget of lies and is completely ill-judged.”