Protesters converge at B.C. Premier Gordon Campbell's Vancouver constituency office on Thursday, urging the return of three children to their parents. (CBC)

More than a dozen people held a peaceful protest outside B.C. Premier Gordon Campbell's Vancouver constituency office Thursday, calling for the return of three children taken from their parents.

The children were seized in September 2007 by the Ministry of Children and Family Development because the Surrey couple were suspected of shaking their baby and causing a head injury.

CBC News is not naming the couple in order to protect the identity of the children — two boys aged four and three, and an 18-month-old baby girl.

"We're being treated as criminals and we did nothing wrong," the mother told CBC News.

The couple said they have been fighting to get back their children, who are now in foster care.

They said their daughter's head was accidentally injured. Their second son "tripped and he landed over her body, and his head landed on her head," the mother said.

This Surrey couple, who CBC decided not to name, say they never hurt their 18-month-old daughter. (CBC)

The baby became very ill and was rushed to hospital by the parents.

They say they took the baby to hospital several more times and saw several doctors over a three-week period before a doctor at BC Children's Hospital concluded someone had shaken her.

That prompted the Ministry of Children and Family Development to take away all three children, even though the RCMP investigated the allegations but decided no charges were warranted.

But social workers with the ministry maintained the parents were unfit to care for their children, referring to the father as a person who has a temper, gets stressed out when the kids cry and may have spanked them.

The dozen protesters said Thursday that parental rights are not protected in the province's child-care system.

"To have people think you are guilty when you treasure your children, that is one of the worst accusations that anybody can say to a parent," the mother said.

The couple consulted more than a dozen experts in Canada and the U.S. — including pediatricians and pathologists — who all concluded there was no evidence of inflicted injury, abuse and injury from shaking on the girl.

B.C. Children Minister Tom Christensen says social workers do not take chances with children's safety. (CBC)

"[My daughter] has absolutely no neck problems whatsoever and the doctors said … if you shook a baby with any force whatsoever you are going to damage the neck," the father said.

Children and Family Development Minister Tom Christensen said Thursday that social workers do not take chances with children's safety.

"There is nothing worse that could happen to somebody as a parent than their children being apprehended," Christensen told CBC News.

"Having said that, I also know that our social workers don't take these steps lightly. It's why they only intervene where there is a concern about a child's safety."

The couple, who now work as night janitors, have begun a legal challenge against the ministry's decision. But they said they likely won't get their day in court until sometime next year, due to delays and backlogs in the court system.

"You are put in a position where you are forced to betray your children's trust," the mother said. "They rely on you for safety and security. We've been forced to betray that."