The Bureau of National Investigations (BNI) on Monday invited Mr Herbert Mensah, a businessman and close associate of former President Jerry John Rawlings, as it investigates his claims of an alleged tape that says President John Evans Atta Mills' campaign team has a budget of GH¢90 million for the July 8-10 primaries of the ruling National Democratic Congress (NDC).
The BNI invited Mr Mensah on Monday morning and he is being questioned by investigators.
A government source has confirmed that Mr Mensah has written a statement and is being interrogated.
Mr Mensah kicked up a huge storm last week when he alleged that he had seen a security tape, which suggests that the huge amount had been budgeted for the Mills campaign for the primaries.
Security experts are concerned about the security tape story, saying if it were true, it would mean the President and the country were not safe.
The Nana Konadu camp has also alleged that the Mills camp was wooing delegates with votes and intimidating their supporters.
President Mills laughed off the GH¢90 million allegation and directed the BNI and the security agencies to investigate the claim.
He said if he had that much available to him (about US$60 million) he would use it for development projects that would inure to the benefit of the people to boost his Better Ghana agenda.
The latest developments widen the gulf between the Mills and Rawlings camps as the NDC prepares to go to congress in Sunyani to elect a flag bearer for the December 2012 presidential election.
There have been accusations and counter accusations between the camps of the two main rivals, President Mills and Nana Konadu Agyeman Rawlings, which are threatening to bring down the ruling party. Former vice chairman of the NDC, Dr Ekwow Spio-Garbrah, another known pro-Rawlings member of the party, also joined the flag bearer race late last week.