Gwen Stefani didn't know Blake Shelton "existed" until she got a job on 'The Voice'.

Gwen Stefani and Blake Shelton

Gwen Stefani and Blake Shelton

The No Doubt singer has been smitten with the country singer since November 2015, and though she is his "biggest fan" these days, she hasn't always felt like that.

She admitted: "I didn't even know Blake Shelton existed in the world I had no idea.

"I'm the biggest Blake Shelton fan now. I know all of his music."

The 47-year-old beauty - who has sons Kingston, 10, Zuma, eight, and Apollo, two, with ex-husband Gavin Rossdale - is determined for her contestants to do better than her partner's on the new series of the singing competition.

She warned: "He is in trouble this season. I'm about ready to get on him."

And asked by 'Late Night' host Seth Meyers if the competition has ever caused problems in their relationship, she joked: "He's been on the couch a few nights!"

But Gwen is smitten with her "incredible" boyfriend and loves the 40-year-old star's positive attitude to life.

She said: "It's so unbelievable. I love Blake. He's the most incredible guy. Everybody loves Blake and that's the thing, there's no way around it. He's just a sparkly, happy, amazing person."

The 'Used To Love You' hitmaker recently admitted it can be "weird" working on the same show as her boyfriend.

She said: "I was nervous at first.

"I was like, 'Wait, is this going to be awkward? How am I going to act?'

"It's just natural. Sometimes it is a little bit [weird]. We're driving home and I'm like, 'Do you think I should put them together?' And then I'm like, 'Wait a minute! I'm not going to talk to you about this! I don't know if you are the enemy. This is confusing.'