Vernon Mann, the father of Nepinak's two children, said a group of people has been out every night intensively searching for her body near the Disraeli Bridge in Winnipeg.
"We go out on our own and look. My son comes out … I couldn't imagine what would happen if he actually found her," Mann said.
"And we shouldn't have to be the ones that are doing that."
Lamb, 52, has been charged with three counts of second-degree murder in connection with the deaths of Nepinak, 31, Carolyn Sinclair, 25, and Lorna Blacksmith, 18.
Sinclair's body was found in a dumpster behind an apartment complex on Notre Dame Avenue in March, while Blacksmith's body was found in a yard on Simcoe Street late last week.
The body of Nepinak, who went missing last September, has yet to be found but police believe she is dead.
Her sister, Gail Nepinak, has said Lamb told one of her family members the body is somewhere near a river. Mann said the area is believed to be near the Disraeli bridge.
But police are ignoring that information, he said.
"My kids have been asking me why the cops aren't searching for their mom's body when they're searching for all these other bodies? And I don't even know what to tell them," Mann said.
His son is 15 and his daugher is 10.
Mann has also accused the police of not keeping the family up to date on their investigation.
"They won't give me any information. I just keep reading about it," he said.
"And I like to know first hand so that if there's something, I can sit down with my kids and tell them … so they don't have to read about it."
Police ground search continues
Meanwhile, police are continuing to conduct ground searches in the city core as part of the investigation involving Lamb. They scoured the West End and parts of downtown on Thursday.
Friday's search will focus more on the areas north of there, around Higgins Avenue and Main Street as well as Selkirk Avenue and the CN tracks.
Officers from missing persons, canine and patrol units are all part of the search, which is being done on both public and private property.
Police are asking that members of the public, including the media, allow for a minimum of 15 metres working distance, in order to give officers and police dogs the "best possible working environment."Suggest a correction