A DAD and his six-month-old son have been found dead in car in a suspected murder-suicide close to where cops caught him drink-driving.

Council workers found the bodies of baby William and his 46-year-old father in a red Holden Commodore on an isolated forest track on Australia’s Sunshine Coast.

The gruesome Wednesday morning discovery was made two days after the child was reported missing.

Police said the father, identified only as a Redcliffe man, failed a breath test after being caught speeding on the Monday, not far from where the bodies were found in the Queensland forest.

The father was let off with an infringement notice after telling police a “sob story”, Nine News reported.

No weapons were found in the car and the cause of the deaths is yet to be established.

The details of the story the man gave are not known, and it is unclear whether the father was pulled over after his baby son was reported missing.

Police sources told Nine News the officer looked inside the car with his torch but didn't see the child and is said to be devastated over what happened afterwards.

Queensland Police refused to comment.

A spokesman told the Daily Mail Australia: “This matter is subject to a coronial investigation which will consider all aspects of the incident including the police response.”

William's shattered family said his mother had been “let down” by the justice system.

The baby boy's aunt Katie Buckingham said the child's death was the “saddest day for everyone involved” and that his mother was “devastated”.

She said: “This should never have happened! The courts have let her down and not kept the baby's father away from her son!”

“Now this beautiful and innocent baby boy has been taken from her by the man who did nothing but make her life hell.”

A GoFundMe page has been set up to help the mother with funeral expenses.

Police said the bodies had been in the car for “some time” before being found, and Daily Mail Australia understands a witness told investigators a car fitting the same description had been parked in the same location on Tuesday.

Det Insp Drinnen said the mother and father had recently separated.

The baby's father was due to hand the child over to his mother as part of a custody arrangement, but never arrived.

No amber alert was issued, despite the child being missing for more than 36 hours.

Police are investigating why the alert - which broadcasts a photo of a missing child to media outlets - was never issued.