The special prosecutor handling the alleged criminal offences in Bountiful, B.C., has resigned.
In a written statement, Attorney General Shirley Bond said Richard Peck is taking himself off the job.
"I have been informed by the assistant deputy attorney general for the criminal justice branch that Richard Peck ... no longer desires to continue on in his role as a special prosecutor for the province with regard to possible criminal offences that have occurred in Bountiful, B.C.," she said.
The statement did not say why Peck stepped down from the post.
RCMP continue to investigate allegations that underage girls were transported between the polygamous community of Bountiful and the United States. Police are looking into "serious criminal offences, including child sexual exploitation, sexual assault and procurement," said the statement.
Bond said the special prosecutor's role is to review police reports received as a result of the RCMP's investigations, and to determine if criminal charges are warranted and carry through with the laying of charges.
"I anticipate that, in keeping with the usual practice of the criminal justice branch, if the special prosecutor decides that there is not a substantial likelihood of a criminal conviction or that a prosecution is not in the public interest, the branch will issue a statement summarizing the reasons of the special prosecutor for that decision," she said.
'Very concerned about these allegations'
Bond said a new special prosecutor will be appointed as soon as possible.
"As attorney general, I am very concerned about these allegations," she said.
"As such, today, I have sent a letter to the assistant deputy attorney general instructing him to appoint a new special prosecutor. It is my understanding that [he] intends to proceed quickly with this new appointment."
In December, B.C. Supreme Court Justice Robert Bauman upheld Canada's polygamy laws, ruling the ban on polygamy infringes on some sections of the Charter of Rights and Freedoms, but also that the criminalization of polygamy is justified.
Bauman spent several months hearing testimony and legal arguments about whether the 121-year-old ban on multiple marriages is constitutional.
The constitutional test case was prompted by the failed prosecution of two men from Bountiful who were charged in 2009 with practising polygamy.