Dean McDermott thinks "monogamy is hard".

Tori Spelling and Dean McDermott

Tori Spelling and Dean McDermott

The 52-year-old actor has been married to Tori Spelling since 2006, but he's conceded that remaining faithful to his wife is a challenge.

Dean - who has kids Beau, two, Finn, seven, Hattie, eight, Stella, 11, and Liam, 12, with Tori - told Us Weekly: "Monogamy is hard for, I guess, several reasons - for wanting that initial lust that we have intrinsically built into us.

"Men, we're like, we need to spread our seed everywhere. It's [been] in our DNA for millions and millions of years. There's that, but then there's also, 'Oh, God. This relationship is work.' And it is.

"Every relationship is work and when you get to that point, you can't bail. You've gotta knuckle under and work it out."

Dean - who also has a 21-year-old son called Jack with his first wife Mary Jo Eustace - admitted it's tough to sustain a relationship when you're living your life in front of the world.

The star - who appeared alongside his wife in the reality TV series 'True Tori' in 2014 - reflected: "We've been doing this for a long time now. You know, 15 years for me, and Tori's been under the microscope since she was a kid.

"I've gotten to the point where Tori's at now, where you just ignore it and you have really thick skin about it, because it really will eat you up.

"And when you are under the microscope and something comes out you think everybody walking in the street thinks the same thing. You feel like, 'Oh my God, everybody knows what's going on. Everybody knows how I'm feeling.' It can drive you crazy."