Chancellor George Osborne has said he wants the new regulator, the Financial Conduct Authority, to "look at the whole package" of charges for payday loans.
He said this would include considering a cap on arrangement fees and penalties as well as the interest rates, in order to put a "cap on the total cost of credit".
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The Labour leader did not say whether he would maintain Britain's nuclear deterrent programme.
Ukip leader Paul Nuttall also said he would want to get rid of Sharia courts.
Over 40,000 people picked up their packs to take part in the annual marathon in the capital.