LONDON (Reuters) - Motormile Finance UK, a debt purchase and collections company, has been ordered to compensate 500,000 customers and write off 414 million pounds ($509 million) in debt by the UK markets regulator over historic systems and controls failures.

The Financial Conduct Authority (FCA) said on Wednesday that customers, who had been pursued unfairly for debt recovery, would receive 154,000 pounds cash after Motormile failed to properly check how much customers owed.

Motormile, which also trades as MMF, MMF Debt Purchase and MMF UK, has since amended its processes, systems and controls. It has rolled out a bespoke new IT system, appointed a new chief executive and has agreed to the compensation package.

($1 = 0.8134 pounds)

(Reporting by Kirstin Ridley; Editing by Mark Potter)