Alan Duncan, from Scotland, is reportedly fighting IS in Iraq and has blasted the UK Government's response to the extremists as "shameful".
Speaking to BBC Radio 5 Live from Duhok in Northern Iraq he defended his decision to go and fight the militants.
He said he had to go and stand up for the "humanity and the Kurdish people" and said Islamic State jihadis were "the most disgusting people since the Nazis".
The BBC said he was training Christians to tackle the militant group which has persecuted tens of thousands of believers as it advances across Iraq and Syria.
"I wear the Union Jack on my uniform. The others wear their flags and what have you," he said.
"It actually lifts the spirit of the people. They kind of feel that, just seeing us foreigners here, it lifts their spirits. They feel that they have been abandoned by the West.
"The British Government disgusts me. I'm a massive Tory, yet my Government is shameful. It's their lack of action in this country. Their lack of action to help Kurdish people."
In a statement the Home Office said: "The UK has consistently advised against all travel to Syria and parts of Iraq. Anyone who travels to these areas is putting themselves in considerable danger."
