The Casino Advisory Panel's (CAP) provisional shortlist of eight proposals excluded the Birmingham site when it was announced last month.
The decision has dashed outgoing chief executive Andrew Morris' hopes of securing a super casino as a legacy before his departure this year (Event, May).
"We were extremely surprised and disappointed at the CAP's decision given the natural fit of a regional casino with the NEC's core business and the site's unique location and capability to attract visitors from across the UK and internationally," said NEC Group marketing and communications director Deborah Smith. "We intend to submit further evidence to the CAP regarding the tremendous potential benefits of the NEC site and urge it to reconsider its decision."
Two London bids, Greenwich's Millennium Dome scheme and Brent council's Wembley project, have made the shortlist for regional casinos. They will compete with Blackpool, Cardiff, Glasgow, Manchester, Newcastle and Sheffield to secure the right to build Britain's first Las Vegas-style super casino.
The winning region will be announced in the autumn.
Despite losing out on the super casino, the NEC remains one of 31 bids shortlisted to house a large casino. Smith added: "There is a very real possibility of securing one of the eight large casinos on offer. We will continue to work hard to convince the CAP of the compelling merits of our location to ensure we are still able to bring a world class entertainment and gaming facility to the NEC."