Forbes' heavy workload and conflict with Governor Darling led him to take 12 months sick leave in 1836-37. While supposedly convalescing in England, Forbes agreed to give evidence at the Molesworth Committee on Transportation. This committee was reviewing the transportation of convicts to the Australian colonies. He spoke forcefully against the practice of internal transportation, whereby convicts who misbehaved were sent to secondary prisons such as Norfolk Island. While not directly opposing the convict system, he tried to argue for a more humane and less harsh method of punishment.