Police are interviewing the parents of an 11-month old boy whose body was discovered in a car outside a day care centre in Perth's eastern suburbs.

It is understood that the child's father arrived at the LadyBugs Day Care Centre in Helena Valley to collect the boy at about 4:00pm (AWST).

When staff told him the boy was never dropped off, he rushed to his car and discovered the baby in the capsule in the back seat.

Paramedics tried desperately to revive the boy but were unsuccessful.