"Disclosure could reasonably be expected to cause prejudice to the defence and the security of the Republic," the SSA says in a letter sent in response to Maynier's request to obtain a copy, a request he made in terms of the Promotion of Access to Information Act.
Maynier, who said the refusal to supply the information reflected a "new paranoia which is spreading like an oil slick in government", released a copy of the letter, dated September 21, on Monday.
In it, the SSA also says that allowing access to a copy of the presentation "would reveal information supplied in confidence by or on behalf of another state or organisation".
Presentation on protection of information bill
The presentation - made last month by State Security Minister Siyabonga Cwele and a senior member of the SSA - dealt with the controversial new protection of information bill.
Maynier said in a statement that members of the media had attended and reported on the presentation, and a detailed minute of the meeting was published on the Parliamentary Monitoring Group's website at the time.
"After the meeting, the minister surprisingly refused to make hard copies of the power-point presentation available to committee members because the document was 'classified'.
"To refuse access to the... information... which was presented at an open parliamentary committee meeting, at which the media were present, is bizarre," he said.
For that reason, he had submitted the request for the document under the Promotion of Access to Information Act. This too had been refused.
"The DA will therefore appeal the decision in terms of the... Act," Maynier said.