The Conservative Party is holding its 2009 event at Manchester Central and it is due to end on 8 October.
Manchester Central head of marketing Sharon Leeson said the conference had attracted thousands of delegates to Manchester. The exact attendance is yet to be released by the Conservatives.
"We have been working hard to invest in our facilities so that we can attract more events of this size and bring further investments to Manchester by helping drive business tourism to the city," said Leeson.
The conference included a speech on the economy by shadow chancellor George Osborne today. Party leader David Cameron is due to address the conference on Thursday.