No Doubt have a "weird process" to making their albums.

The ska-pop band announced in January they have begun recording sessions for their first album since 2001's 'Rock Steady', but singer Gwen Stefani has warned it will take some time to complete.

She said: "My band takes a weird process. It takes so long. And all of them just had babies, so it'll be a while."

The group's guitarist Tom DuMont announced the arrival of his and wife Mieke's third child this weekend, while bass player Tony Kanal welcomed his first daughter with girlfriend Erin Lokitz in January.

No Doubt - completed by drummer Adrian Young - have been working on new material since ending a hiatus in 2008, and despite warning of a delay before release, Gwen, 41, said significant progress has been made in recording.

She added to the Wall Street Journal: "We've been doing a record all year; ten songs have been recorded. When this is done I'll go probably write a few more songs.

"I don't know when it'll come out, but you never know what can happen. I sang on three of them. One of them I might not re-sing."

The band are thought to be aiming to release their sixth album before the end of the year.