Country singer Blake Shelton is adamant he doesn't deserve a songwriting credit on his festive collaboration with girlfriend Gwen Stefani.

The Honey Bee hitmaker joins the No Doubt frontwoman on her track You Make it Feel Like Christmas, and although Gwen has heaped praise on her man for helping her come up with the right words for the romantic tune, Blake insists his lyrical contribution was minimal.

"I sent Gwen a couple of lines of the song. She took it and made the song what it is. I just sent her an idea," the humble star told Entertainment Tonight. "She tries to say that I co-wrote it, but I just sang on it."

The holiday love song originally featured as the title track on Gwen's 2017 Christmas album, but was recently re-released with a festive video, in which the couple sings lines like, "I never thought I'd find a love like this/But I found forever in that very first kiss," leading many fans to wonder if the words are all about the pair's own road to romance.

Asked if there's any truth to the song speculation, Blake smiled, "I would like to think so, come on! This is romance around here, of course!"

The singers have been dating since 2015, following the breakdown of Gwen's marriage to rocker Gavin Rossdale, and Blake's divorce from fellow country star Miranda Lambert, and the couple has been inseparable ever since.

Blake and Gwen have been splitting the majority of their time between his ranch in his native Oklahoma and the mother-of-three's home base in Los Angeles, and although he knows they will be spending Christmas together, he has no idea where the celebrations will be taking place.

"She normally just tells me what we're doing," Blake shared. "So, I couldn't tell you what they (plans) are, yeah, (but) just wherever she is, I'll be there."