Ballymena soldier Blane Millar – thought to be the youngest of 7,600 British troops in Afghanistan – was praised as "incredible" by the Tory leader during his keynote closing address to the Conservative party conference.

Mr Cameron met Blane – who was sent to fight days after turning 18 in April – during a visit to British troops in Helmand province last month.

In a speech broadcast around the world Mr Cameron told his audience: "Up the Helmand river, in a place called Sangin, I met a soldier in the Royal Irish Regiment, Rgr Blane Millar.

"He had only just turned 18 years old. He was the youngest soldier there.

"He's not much more than a boy and he's there in the 45 degree heat, fighting a ferocious enemy on the other side of the world.

"I said to him: 'You are doing an incredible job'. And I remember he just said: 'I'm just doing my duty'."

Rgr Millar's parents Martin and Karen, who were both at work as Mr Cameron was speaking, told of their pride and revealed that Blane and his comrades had watched the speech on television at their base in the Afghan desert.

"I'm very, very proud of him," said Martin.

"Blane phoned just before the speech to say they were watching it on the big screen they have in the camp. Apparently it went down really well with the soldiers.

"He was delighted by it. He said they all cheered and clapped when it happened, but he just couldn't believe it."

Martin explained how his son had learned of Mr Cameron's intention to name him at the conference: "Blane phoned me on Monday evening and said that they had guard duty in three hours, so he was going to lie down.

"But then he phoned me back an hour later and said that his sergeant was in and he was called to the operations room.

"His commanding officer was there and said that because he was the youngest soldier in theatre and he had met David Cameron, that he wanted permission to use his name, age and regiment in the speech."

On Tuesday night, aides to Mr Cameron said the speech was being drastically rewritten to take account of the global financial catastrophe, but his words of praise for the young Ulster soldier were not removed.

Rgr Millar, who is fighting with the RIR's 1st Battalion, is to return soon from his dangerous six-month mission.

Martin said he was looking forward to his son's return: "Blane went out about 10 days to two weeks after he turned 18. I think they were just so short of troops that they were pushing them out there really early.

"When he spoke to David Cameron he asked him what he missed and Blane said it would be good to get back home and be able to have a drink with my mates because since he'd been training he had turned 18, but hadn't really had that chance."