Longworth was suspended following an emergency board meeting on Friday night, reports the Financial Times, following remarks which do not reflect wider feeling amongst many of the BCC's members.
On Thursday Longworth became one of the first major business leaders to back a Brexit when he told Sky News that "the UK would be better off taking a decision to leave the European Union".
Earlier, in a keynote speech at the BCC annual conference, he said: "The dynamism and resilience of the City of London and the UK business sector suggests to me that, in the long run, we have the capacity and capability to create a bright, if not brighter, economic future outside of the EU - just as we would have done had we had the opportunity to stay in a truly reformed Europe."
In a statement the BCC said it would not campaign either way ahead of the June 23 referendum as its membership was split.
"The BCC will survey chamber member companies across the UK, report their diverse views, and inform the debate," it said in a statement.
“The BCC’s director general has been very clear where his remarks reflect his personal assessment, rather than the position of the BCC.”