It has run for a decade, pulling in television audiences of more than six million with its counter-terrorism plots, bed hopping and unexpected deaths. But according to former secret service agent and bestselling author John le Carré, the BBC series Spooks is "crap".

Speaking at the premiere of the new film version of his classic spy novel Tinker, Tailor, Soldier, Spy, Le Carré said that the MI5 drama was unrealistic. "If you have lived in that world, you know that it is stupid. I don't watch Spooks. It's crap. I'm sorry. I have been in that world for almost half a century and once in it, you get a notion of what constrains you and what doesn't," said the author, who worked for years as an agent for MI5 and MI6.

"The idea that people just go around shooting and killing people and so on is crazy," added Le Carré. Spooks is renowned for killing off characters: in the first series, a lead cast member died when her head was plunged into a deep-fat fryer.

"If I was working at sea, I would have written about the navy," the author said yesterday. "But that was my reality during my most formative years and to see it sadly traduced and made comedic or turned into a kind of bus ride of fast cars and fast women is just junk."

Creator of the spymaster extraordinaire George Smiley – "Small, podgy and at best middle-aged, he was by appearance one of London's meek who do not inherit the earth" – Le Carré's debut novel, the spy thriller Call for the Dead, was published in 1961. He first received international acclaim for 1963's The Spy Who Came in From the Cold, and today is the author of 22 novels. Gary Oldman is playing Smiley in the new version of Tinker, Tailer, Soldier, Spy, which Le Carré – the penname for David Cornwell – first published in 1974 and which was previously adapted in 1979, starring Alec Guinness as the spy Smiley.