Why was the 19th century indenture system

Why was the 19th century indenture system referred to as the ‘new system of slavery’?

The indentured labourers lived in harsh working conditions and had few legal rights.
On arrival at the plantations, labourers found conditions to be different from what they had imagined. They had to work like bonded labour. If anyone wanted to run away, he was caught and severely punished.