Police are investigating after a grandmother's expensive oak coffin was switched to a cheaper box for cremation, following a funeral service in central Queensland.

Janice Valigura, 74, died on New Year's Eve and was farewelled at a funeral service in Rockhampton on Monday.

Her family had bought a top-of-the-range silky oak casket as part of the funeral package.

Ms Valigura's son Mick said they were told there would be a delay in moving the body from the church to the crematorium.

Janice Valigura was farewelled at a funeral service in Rockhampton on Monday. ( Supplied )

But when the family arrived at the crematorium one of the mourners noticed the casket had been swapped for a cheaper box.

Mr Valigura said the family was devastated but the undertaker told him it was common practice.

He said police officers had taken photos of both coffins as part of an investigation.

Detective Sergeant Craig Strohfeldt said it was the first time Rockhampton police had heard of such allegations.

"I've never received a complaint of this nature — it's quite unusual," he said.

He labelled the complaint "shocking" and said police were taking it seriously.

"It is quite a serious matter and we're putting a lot of resources into the investigation," he said.

The funeral director has denied any wrongdoing but declined to comment.

Calls for industry regulation

Queensland Funeral Directors Association president Anton Brown said it was not normal procedure in funeral homes.

"It's like buying a Mercedes and getting a Toyota Corolla, that's not common practice" Mr Brown said.

He said he felt bad for the family involved and called it "disgraceful".

"When people choose a funeral director they put a lot of trust in the person. This person who has done this to the family has broken their trust," Mr Brown said.

Whitsunday Funerals and Crematorium director Jeff Doyle has previously raised concerns about standards in the industry, and has written to the Premier and Attorney-General.

"This is the sort of thing that's probably common practice around Australia," he said.

"But unfortunately because most crematoriums, you're not allowed to go down and actually see the coffin go into the cremator, it's easy for them to do it.

"I feel sorry for the family in Rockhampton, I really do.

"I've been trying to get this out a long time.

"The industry needs serious regulation and it needs to be an independent, non-government board that actually inspects funeral homes."

Anton Brown said he would also like to see the industry regulated but said previous concerns raised with the government had fallen on "deaf ears".