Britain’s increasingly hard-left Labour party is coming under pressure over its stance on defence and NATO, as the military alliance celebrates its 70th anniversary with a major conference of member heads of state in London.

Labour leader Jeremy Corbyn has a long record of criticising Britain’s membership of the NATO alliance — the largest and longest-standing military alliance of its kind in world history — a position of standing against what he characterises as Western “Imperialism” that he once also held for the European Union.

Questioned on these positions and hence his fitness to be the leader of the United Kingdom, a nuclear power and leading member of NATO, Labour spokesman Barry Gardiner opted instead to double down, criticising the alliance as having been on the wrong side of history.

Speaking on Britain’s state broadcaster the BBC on Wednesday morning as NATO leaders gathered outside of London for the second day of the NATO summit, Mr Gardiner said NATO had engaged in “phony defence… aggressive militarism” and would take a different direction of de-escalation with Russia if Labour controlled the British government.

While Mr Gardiner emphasised the Labour election manifesto stated the party had a “clear commitment” to NATO, he became riled when questioned on the BBC Today programme about Jeremy Corbyn’s recent-past comments on the alliance, including when Mr Corbyn accused it of promoting a “cold war”. He has also said NATO had no place in a “world of social and economic justice” in an article for the Communist-founded Morning Star newspaper.

Accusing NATO of having been on the wrong side of history, Mr Gardiner told the BBC: “The way you defend this country is by ensuring you don’t go on foreign wars, you don’t start bombing before you’ve started thinking. Consistently if you look at the Iraq war, who was on the right side of history on that? Jeremy Corbyn was.

“Not the President at the time, and indeed not the Labour party at the time under Tony Blair. But all of Parliament went into that, Jeremy Corbyn did not. If you look at Libya… if you look at the way we want to use a defensive alliance, it is to think carefully through positions, learn the lessons of the Chilcott report, learn how you should try and prevent conflict and de-escalate a situation rather than promote a conflict.”

The comments come at a time where U.S. President Donald Trump has questioned the commitment of many NATO members, who have been — in his words — “delinquent” on defence spending for years, and even decades. The NATO treaty requires members to spend a minimum of two per cent of national GDP on defence, a measure to ensure fair but equal burden sharing between all members.

In reality, few members hit the minimum requirement, with economic powerhouse Germany standing out as a particular offender, coming in for regular criticism from the President over their lack of commitment to their allies.

President Trump and other leaders and defence ministers of the NATO member states are in the United Kingdom today for a conference to mark the 70th anniversary of the alliance. While the treaty signing the alliance into existence was signed in New York in 1949, NATO’s first meeting was in London that year.