Singer Gwen Stefani's fashion empire is going to the dogs - she is expanded into pet clothing.

The Hollaback Girl star has teamed up with designers at Petco to launch the Harajuku Lovers collection, which features dog toys, clothing, accessories and hats inspired by her Harajuku Lovers clothing line, which she created in 2005.

Despite her success in the fashion industry with her labels, Stefani admits she had to work hard to convince bosses at the company to let her design a collection for pooches.

"I wanted to do this collection for so long because the people that I work with around me that I love, they wanted so desperately for me to do a line of dog wear and toys and things like that," she tells People.com. "And it's really hard - we had to really stalk them to let us do it, and we got it and so now, here it is and it's really exciting."

The 20-piece collection features designs linked to her early days with rock band No Doubt.

"We went back to the beginning of time when I first discovered music and was really into discovering ska music, (and) music out of England," she continues. "And that was the reason we started doing No Doubt, so you can see the British flag and the record and you can see (it in) the little hat and checkerboards and things that just represent that time period."

"There's also the old with the new," she adds. "At the time that I was designing the collection, I was doing (song) Spark the Fire with all the emoji (characters) and things like that, so you can see that in the hair accessories... It's kind of a combination of old and new (influences) through the years."