Rep. Thomas Murt asked for an explanation from the state attorney general and labor secretary, neither of whom immediately offered a response on Wednesday.
"It appears those permits were granted even though the law does not provide for them," Murt said in a statement.
The TLC program "Kate Plus 8" is filmed in Wernersville, Pa., about 55 miles northwest of Philadelphia, and follows the lives of Gosselin and her twins and sextuplets. Its predecessor, the popular "Jon & Kate Plus 8," featured the family before the parents divorced.
Murt, a Republican from suburban Philadelphia, held a legislative hearing in April on the need to update child labor laws in the age of reality TV and Internet entertainment. Kate Gosselin's estranged brother testified that he worried about the psychological effects that constant filming might have on his nieces and nephews.
The same day, the Department of Labor & Industry released findings of an investigation into "Jon & Kate Plus 8." Regulators ruled that producers should have obtained labor permits for the Gosselins' children during the years of filming here.
No penalties were assessed as long as permits were obtained for future filming and a portion of "Jon & Kate" proceeds were placed in a trust fund for the kids.
Later in April, Figure 8 Films obtained six-month permits from the labor department that limit the hours and conditions of filming the youngest Gosselins for "Kate Plus 8."
But Murt, who last month introduced a bill to reform child labor laws, believes current regulations allow children under 7 to participate only in movie productions.
He sent letters Tuesday to Labor & Industry Secretary Sandi Vito and Attorney General Tom Corbett asking for clarification.
A spokesman for Vito said the department's attorneys were reviewing the letter. A Corbett spokesman did not respond to a request for comment.
Alisha Agemy with Figure 8 Films referred questions to TLC/Discovery, which declined to comment Wednesday.
A lawyer for Kate Gosselin did not immediately return a message.