VANCOUVER — The brother and sister of convicted serial killer Robert Pickton are suing the attorney general and solicitor general of British Columbia over the farm where RCMP found remains of the six women he was convicted of murdering.

The lawsuit filed by David Pickton and Linda Wright claims the RCMP search of the farm where Pickton lived in suburban Coquitlam severely damaged the property.

"As a result of the said actions by the RCMP the Properties are presently useless and the plaintiffs have suffered significant loss and damage," said a writ of summons filed this week in B.C. Supreme Court.

David Pickton declined comment Thursday.

In the lawsuit, the siblings said the RCMP promised them compensation for damages but they haven't received any.

They claim the search excluded them from properties they had lawful rights to use and they accuse the RCMP of demolishing, removing, destroying or rendering uninhabitable various buildings and equipment on the property.

"Further, in the course of that investigation the RCMP disturbed, disrupted, killed and destroyed various plants, trees, groundcovers and other vegetation and the fish in the pond on the properties," the lawsuit said.

"The actions of the RCMP aforesaid were done in violation of the rights and interests of the plaintiffs, or alternatively were done negligently."

The two Pickton siblings, who owned the property jointly with their brother, are seeking damages, cost and interest from the province.

A spokesman for Attorney General Wally Oppal said the department hadn't yet seen the writ of summons and could not comment Thursday. RCMP also declined comment.

The province has a $10-million lien on the property to secure recovery of legal costs for Pickton's trial.

Friends and family of the murdered women have said they'd like the property turned into a memorial park.

Forensic experts and archeologists spent months combing the 4.5-hectare property, uncovering gruesome evidence presented at trial.

Pickton was convicted in December 2007 on six counts of second-degree murder following am 11-month trial and several years of pretrial arguments.

Pickton is now serving a minimum 25-year prison term for the murders of Mona Wilson, Marnie Frey, Georgina Papin, Brenda Wolfe, Sereena Abotsway and Andrea Joesbury.

The B.C. Court of Appeal is set to hear appeal arguments on the case starting March 30.

Pickton initially faced 26 first-degree murder counts, but the trial judge separated the charges into two trials to simplify the process.

If the Appeal Court upholds the six convictions, the B.C. Criminal Justice Branch will drop its plans for a trial on the remaining 20 murders Pickton stands accused of committing.

If the court orders a new trial, the Crown wants all 26 first-degree counts to be heard at once.