Two West Midland MPs are demanding the government reconsiders the NEC's bid for a super-casino.
The NEC casino bid will be raised in Parliament
The call comes after allegations that the Deputy Prime Minister John Prescott helped a rival bid.
Mr Prescott denies breaking ministerial codes when staying in the ranch of the Millennium Dome owner, who wants to build the UK's only super casino.
Conservative Andrew Mitchell and Lib Dem Lorely Burt are to raise a challenge in Parliament.
Ms Burt believes the NEC bid, in Solihull borough, has to be looked at again.
The Solihull MP told the BBC: "I thought that the original decision was absolutely incomprehensible and what I would like to see is more transparency in how the decision was actually arrived at by Mr Prescott."
There were also regional bids based on Birmingham City FC's ground and the Ricoh Arena in Coventry.