By Jill Serjeant

LOS ANGELES (Reuters) - The mother of pop star Britney Spears on Wednesday heaped the blame for her daughters' erratic behavior throughout 2007 and early this year on herself in a television interview saying "it's always my fault."

Appearing on the morning TV talk show "Today" on NBC, Lynne Spears also said that she first thought it was joke when her younger daughter Jamie Lynn announced she was pregnant at age 16 -- in a note.

"It said she was pregnant and everything was going to be OK. She was going to raise it ... I thought it was a joke. I was waiting for the punch line," Lynne Spears told interviewer Meredith Vieira.

"I was in shock. I think I was just truly in shock, and then I started to cry. And she started consoling me at that point."

Jamie Lynn gave birth to a girl in June and is raising the baby with her boyfriend in their Mississippi home.

Spears, 53, said she accepted much of the blame for the crises of the past two years. Britney shaved her head, went in and out of rehab, lost custody of her children and was hospitalized in a psychiatric ward.

"As a mother, don't we always blame ourselves?" she said. "I took a lot of the blame. I took all the blame. The personality I have, it's always my fault."

Spears has written a memoir, "Through The Storm" which is being published this week, about the rise to fame of her daughters.

She said her family had no idea how difficult life was to become after Britney had her first hit, in 1998, with "Baby One More Time" at the age of 17.

"There's the honeymoon phase at first," Lynne Spears said. "Everything is fabulous. Look at the wonderful trips she gets to go on. Look at the wonderful people she's meeting.

"Then there's the ugly side of things that turns, and we weren't ready for that, either."

Britney Spears, 26,, has turned her life around in the past six months with her father now managing her affairs and a new album due out in December. Looking fit and glowing, she won three MTV video music awards last week.

"She's strong," Lynne Spears said. "She's resilient. She's had some big bumps in the road, but Britney's fine. Britney is headed to the top once again. I have no fears about Britney."