Jeremy Corbyn appeared to remain silent during the anthem
A spokesman said: “Jeremy attended today’s event to show respect for those who fought in conflicts for Britain.
“As he said in the words issued this morning, the heroism of the Royal Air Force in the Battle of Britain is something to which we all owe an enormous debt of gratitude. He stood in respectful silence during the anthem.”
The commemorations marked the 75th anniversary of the battle - which took the lives of 3,242 aircrew and about 40,000 civilians.
Pictures taken of Corbyn showed the 66-year-old keeping his lips firmly sealed as God Save the Queen was played. The Labour leader looked solemn with his hands clasped in front of him.
His decision not to sing has been criticised by some, including Conservative MP Sir Nicholas Soames - the grandson of Winston Churchill - who said it was "very rude and very disrespectful".
Labour's new shadow work and pensions secretary Owen Smith told BBC Newsnight on Tuesday evening that Corbyn should have sung the anthem.
"I would have advised him to sing it, yes. I would absolutely, irrespective of his views," he said. "I am not sure he didn’t sing it because he is a republican, he may well have been thinking of something else."
"He was about to do his big speech at the TUC, perhaps he was thinking about that. Or more likely, he was thinking about the people he was commemorating."
Article continues below slideshow:
Jeremy Corbyn At Battle Of Britain Commemorations
Britain Battle of Britain Service(01 of09)
Open Image Modal
The leader of Britain's opposition Labour party Jeremy Corbyn, second left, and his deputy Tom Watson, left, arrive for the 75th anniversary Battle of Britain memorial service at St Paul's Cathedral in London, Tuesday, Sept. 15, 2015. The Battle of Britain was an aerial battle in World War II between Allied air forces and the German Luftwaffe in the late summer and early autumn of 1940. (AP Photo/Alastair Grant) (credit:Alastair Grant/AP)
Britain Battle of Britain Service(02 of09)
Open Image Modal
Leader of the British opposition Labour party Jeremy Corbyn, second left, with his deputy Tom Watson, left, arrive for the 75th anniversary Battle of Britain memorial service at St Paul's Cathedral in London, Tuesday, Sept. 15, 2015. The Battle of Britain was an aerial battle in World War II between Allied air forces and the German Luftwaffe in the late summer and early autumn of 1940. (AP Photo/Alastair Grant) (credit:Alastair Grant/AP)
Battle of Britain commemorations(03 of09)
Open Image Modal
Leader of the Labour Party Jeremy Corbyn (second right) during a service at St Paul's Cathedral in London to mark the 75th anniversary of the Battle of Britain. (credit:Jonathan Brady/PA Wire)
Battle of Britain commemorations(04 of09)
Open Image Modal
Leader of the Labour Party Jeremy Corbyn (third left) during a service at St Paul's Cathedral in London to mark the 75th anniversary of the Battle of Britain. (credit:Jonathan Brady/PA Wire)
Battle of Britain commemorations(05 of09)
Open Image Modal
Leader of the Labour Party Jeremy Corbyn (fifth right) and Defence Secretary Michael Fallon (third left) during service at St Paul's Cathedral in London to mark the 75th anniversary of the Battle of Britain. (credit:Jonathan Brady/PA Wire)
Battle of Britain commemorations(06 of09)
Open Image Modal
Prime Minister David Cameron (left), Defence Secretary Michael Fallon (centre) and Leader of the Labour Party Jeremy Corbyn (right) during a service at St Paul's Cathedral in London to mark the 75th anniversary of the Battle of Britain. (credit:Jonathan Brady/PA Wire)
Battle of Britain commemorations(07 of09)
Open Image Modal
Leader of the Labour Party Jeremy Corbyn (right) shakes hands with Defence Secretary Michael Fallon (left) during a service at St Paul's Cathedral in London to mark the 75th anniversary of the Battle of Britain. (credit:Jonathan Brady/PA Wire)
Battle of Britain commemorations(08 of09)
Open Image Modal
Leader of the Labour Party Jeremy Corbyn greets Prime Minister David Cameron during a service at St Paul's Cathedral in London to mark the 75th anniversary of the Battle of Britain. (credit:Jonathan Brady/PA Wire)
Battle of Britain commemorations(09 of09)
Open Image Modal
Jeremy Corbyn during a service at St Paul's Cathedral in London to mark the 75th anniversary of the Battle of Britain. (credit:Jonathan Brady/PA Wire)
His new deputy leader Tom Watson accompanied Corbyn to the service.
In a statement released to mark the ceremony, Corbyn said: “My mum served as an air raid warden and my dad in the Home Guard.
“Like that whole generation, they showed tremendous courage and determination to defeat fascism. The heroism of the Royal Air Force in the Battle of Britain is something to which we all owe an enormous debt of gratitude.
“The loss of life - both civilian and military - should be commemorated so that we both honour their lives and do all that we can to ensure future generations are spared the horrors of war.”
Corbyn's decision to remain silent was not the only cause for controversy during the event; even his attire was picked apart by critics who were unhappy with his appearance.