The mother of a Briton killed fighting for the Kurds against Islamic State has said she is proud of his courage.
At a reception in Parliament, Vasiliki Scurfield said her ex-Royal Marine son Konstandinos was not fighting for Britain but was "certainly supporting British values" when he died.
She said her family had received "stunning and inspiring" support, and called for more action against IS.
Mr Scurfield, 25, from Barnsley, died in northern Syria on 2 March.
His coffin was handed over to his father and uncle in a ceremony involving hundreds of Syrian Kurds on Saturday - something his father Chris called "overwhelming".
'Make a difference'
In her speech at Parliament, Mrs Scurfield said her son Konstandinos Erik "Kosta" Scurfield had left the Royal Marines to join Kurdish fighters.
"Kosta was not a mercenary," she said. "He wasn't an out-of-work soldier looking for an adventure or something to do to pass the time."
She added: "Kosta was determined to make a difference and although this is not a way that many of us would have had him choose, it was the way he considered the best for him and I am proud of him for finding the courage to do this."
Mrs Scurfield said her son wanted to oppose IS militants to protect the "fundamental rights of every human being".
"In other words he was a humanitarian who, in his own words, wanted to help," she said.
She said her son was "not the only hero" and she was not the "only mother who is mourning" - mentioning the hostages, religious and ethnic groups, enemy soldiers and others killed by IS.
"We have found the support of so many people stunning and inspiring," she added.
'Stop standing by'
In a message to British voters ahead of May's general election, Mrs Scurfield said: "If you are feeling politically apathetic but have strong feelings about self-titled IS, then here is a cause and a clear reason to get involved."
She urged voters to ask candidates a range of questions including what they planned to do about IS and why Britain had not given more support to Kurdish fighters.
She likened the Kurds to the "300 Spartans" who resisted the might of the Persian army at the battle of Thermopylae, and said that, though "inadequately equipped", they had shown IS was "not invincible".
"Let's stop standing by and let's instead think creatively about grinding down and putting out the biggest threat to the world since the Nazis," she added.
IS took control of large areas of Iraq and Syria last year, and declared a "caliphate" under its strict version of Islamic law.
Kurdish forces, some of whom had asked to bury Mr Scurfield in Syria "as a martyr", are thought to number about 30,000. The BBC understands that includes about 100 Western volunteers - including some Britons.
At least 500 Britons are believed to have travelled to join IS.
US-led air strikes against IS began in August and more than 2,500 have been carried out so far.
The UK, which is taking part in the air strikes, has supplied Kurdish fighters with machine guns, ammunition and other equipment, and British soldiers have provided some training.