The actor, who plays disgraced spy River Cartwright in the Apple+ drama, said the series was a workplace drama masquerading as a spy thriller.
Lowden said that in making the show, the actors had some interactions with ex-spies.
He said it was “really wonderful” to discover that Britain’s intelligence services really were “full of people bitching about wanting a corner office rather than a cubicle or why don’t they get sexier assignments?”
The actor said he was trained in spycraft by intelligence advisers.
“My favourite thing that they revealed was their reliance on our industry for their recruitment,” he told The Sunday Times.
“TV and film make spies sexy and that’s why people join. I’d love to speak to them now that Slow Horses is out there, making it look grubby and boring.”
Slow Horses is based on Mick Herron’s novel of the same name, which is part of his Slough House series.
It tells the story of a team of misfit intelligence agents banished to Slough House, an MI5 backwater, for failing at their jobs.
Lowden’s character works for Jackson Lamb, played by Gary Oldman.
The actor compared the bumbling pair to Rodney and Del Boy from Only Fools and Horses.
“I was obsessed with Only Fools and Horses when I was a kid and no matter how much those two brothers went through, the writer John Sullivan always whipped the carpet out from underneath their feet,” he said.
“River is constantly feeling that he can change his situation and get back to the sexier side of the track. But each series ends with him back where he started.”
He added: “It’s such a British brand of irreverent comedy developed over hundreds of years.
“That’s why I really hope there is a season where someone comes in from the CIA. I would love Lamb to be sitting in the corner eating a doner kebab while some American is doing something fancy on a whiteboard to do with drones. That is perfect Slow Horses.”
Lowden said it was “bizarre” that it had taken three series of the drama – each of which has received rave reviews – to attract broader attention.
“The reviews have been fantastic, but it’s always difficult when it’s not on ‘normal television’,” he added. “Being on a streaming service gives a show a chance to grow.”