The FA, says Hargitay, whose European Consultancy Network has been awarded the consultancy contract, will end his work for the FIFA President next month "in order to avoid any conflict of interest".
Siegler left FIFA after 12 years in September. In July 2002 he was appointed FIFA's Director of Communications, an executive director of FIFA and member of the FIFA management board.
A spokesman for the FA said in the statement: " We expect a highly competitive bidding process with several countries from three continents already having voiced an interest to bid for the 2018 World Cup, and it is very important we have such international experience working with us."
The Netherlands and Belgium have anmnounced their plans for a joint bid, while Australia, Russia, China, the United States and Mexico are also considering bidding.
