The Chicago Mercantile Exchange and the Chicago Board of Trade contributed a total of $208,000 (€150,000) to the city's mayor earlier this year. The news comes a week after the mayor's office and the State of Illinois pledged $40m to help with the exchanges' merger.

The political contributions were made in January and February as Richard Daley, the democrat mayor of Chicago since 1989, sought re-election for a fifth time, according to the Chicago Sun-Times, a US newspaper.