The "war on terror" has been a failure, Jeremy Corbyn said as he insisted as prime minister he would not be afraid to stand up to Donald Trump's US administration.

In a major speech setting out his approach to foreign and defence policy, the Labour leader said "fresh thinking" was needed.

In an address to the Chatham House international affairs think tank in London, Mr Corbyn insisted he was not a pacifist but cautioned against a "bomb first, talk later" approach to foreign policy.

"Today the world is more unstable than even at the height of the Cold War. The approach to international security we have been using since the 1990s simply has not worked," he said.

"Regime change wars in Afghanistan, Iraq, Libya, Syria - and Western interventions in Afghanistan, Somalia and Yemen - haven't always succeeded in their own terms.

"Sometimes they have made the world a more dangerous place."

He said it was the fourth general election in a row during which the UK had been at war.

"The fact is the war on terror, which has driven these interventions, has not succeeded.

"It has not increased our security at home. In fact, many would say, just the opposite."

Senior members of Mr Corbyn's team were present for the speech, including shadow foreign secretary Emily Thornberry and shadow attorney general Baroness Chakrabarti.

But shadow defence secretary Nia Griffith - whose support for the Trident nuclear deterrent is at odds with her leader - was notably absent from the event.

Mr Corbyn, who has been accused by the Tories of being weak on defence and security, hit out at the way the issue was characterised.

"Too much of our debate about defence and security is one-dimensional, you are either for or you are against what is presented as 'strong defence', regardless of the actual record of what it has meant in practice," he said.

"Alert citizens - or political leaders - who advocate other routes to security are often dismissed or treated as unreliable."

Mr Corbyn condemned Mr Trump's US administration for "recklessly" endangering global security through interventions in North Korea and Syria while opposing President Barack Obama's nuclear deal with Iran.

He said that while a Labour government would want a "strong and friendly" relationship with the US, it would "not be afraid to speak our mind" to Washington.

He criticised Theresa May for "pandering" to the US president during her visit to Washington earlier this year.

"Waiting to see which way the wind blows in Washington isn't strong leadership. And pandering to an erratic administration will not deliver stability," he said.

"Britain deserves better than simply outsourcing our country's security and prosperity to the whims of the Trump White House. So no more hand-holding with Donald Trump.

"A Labour government will conduct a robust and independent foreign policy made in Britain."

He also denounced the way in which Mrs May had spoken in "alarmist terms" about the rise of China and India and the need for Britain and America to use their "military might" to protect their interests.

"That is the sort of language that led us into the calamities in Iraq and Libya and other disastrous wars, that stole the post-Cold War promise of a new and peaceful world order," he said.

Mr Corbyn, a former chairman of the Stop the War coalition, denied that he was a pacifist but said the "bomb first, talk later" approach to security taken by the Conservatives in government had failed.

"The best defence for Britain is a government actively engaged in seeking peaceful solutions to the world's problems. But I am not a pacifist," he said.

"I accept that military action, under international law and as a genuine last resort, is in some circumstances necessary.

"But that is very far from the kind of unilateral wars and interventions that have almost become routine in recent times."

The Labour leader, who has previously made clear he would never authorise the use of Britain's nuclear weapons, said that if it ever were to emerge as a "real option" it would represent a "cataclysmic failure" by world leaders.

"I am often asked if as prime minister I would order the use of nuclear weapons," he said.

"It's an extraordinary question when you think about it - would you order the indiscriminate killing of millions of people? Would you risk such extensive contamination of the planet that no life could exist across large parts of the world?

"If circumstances arose where that was a real option, it would represent complete and cataclysmic failure. It would mean world leaders had already triggered a spiral of catastrophe for humankind."

Mr Corbyn said that in office, Labour would work to halt the "drift to conflict" with Russia while maintaining its opposition to human rights abuses by Moscow.

"There is no need whatever to weaken our opposition to Russia's human rights abuses at home or abroad to understand the necessity of winding down tensions on the Russia-Nato border and supporting dialogue to reduce the risk of international conflict," he said.

Mr Corbyn said Labour would retain the commitment to the Nato target of spending 2% of GDP on defence, and strongly criticised the Conservatives' record on the armed forces.

"They have balanced the books on the backs of servicemen and women. Deep cuts have seen the Army reduced to its smallest size since the Napoleonic Wars," he said.

"From stagnant pay and worsening conditions to poor housing, the morale of our service personnel and veterans is at rock bottom."

For the Conservatives, Defence Secretary Sir Michael Fallon said Mr Corbyn had shown he would put Britain's security at risk.

Sir Michael said: "He says he would never use Trident, dithers over confronting Isis (Islamic State), and wants to tie the hands of our intelligence services.

"Jeremy Corbyn is simply too weak and shambolic to stand up to terrorists and tyrants who want to do us harm."