Jonathan Luff, a senior Downing Street aide, is to leave before taking up a role running governent affairs at Wonga.
Luff has been running a key trade promotion campaign for several months and is not subject to any restrictions on the timing of his move.
It is likely to provoke protest among MPs critical of Wonga's business model that the company will have inappropriate access to ministerial decision-makers.
Mr Luff's appointment comes as the Office of Fair Trading intensifies a crackdown on payday lenders amid concern over the industry's business practices.
Wonga's business model has provoked intense controversy in Westminster because of the interest rates it charges - in some cases, more than 4,000 per cent.
A spokeswoman for Wonga said: ‘Wonga is pleased to confirm that Jonathan Luff is joining the company next month as global head of public affairs.
"There will be restrictions on contact with the government departments where he has worked until the OFT review into the payday lending sector concludes.
"Jonathan has prior Diplomatic Service experience and wide-ranging international contacts, and he is therefore well placed to support the company’s international growth. Wonga is delighted with the appointment, committed to growing a sustainable and responsible digital finance business, and to hiring the best available talent."
