The consumer watchdog has accused payday loan companies of "irresponsible lending", "pressure tactics" and other bad practices.
The OFT has given them them 12 weeks to prove they provide an important service, or else they could face closure.
However, there will be no cap on interest rates.
Consumer Editor Chris Choi reports:
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Almost a fifth of hospital patients were also unable to reach their call button, a report warned.
At least 2,400 cancer sufferers die needlessly every year because their GP does not refer them to a specialist quickly enough.
It comes after shadow chancellor John McDonnell made a surprise U-turn on the Tory budget vote which is due later today.