A city-based Twenty20 tournament could have "far-reaching consequences" for counties who play at non-Test match grounds, says Kent's Jamie Clifford.
Kent have abstained in a vote on a change in rules which would allow the competition to take place.
"Our stance reflects the anxiety among non-Test match grounds. Their role as active players in the game's future is at risk," said Kent chief Clifford.
Middlesex and Essex are the only two to say they will vote against the changes.
The proposed changes to the England and Wales Cricket Board (ECB) articles of associations require the support of 31 of 41 voting members, with the new tournament scheduled to start in 2020.
Clifford added: "While Kent Cricket does not wish to be at odds with the ECB, the proposals for the future direction of the game as they stand are such that the club cannot actively endorse them."
However, while he also accepted it was "inevitable that the proposals will receive the support that they need to be enacted", he wants Kent to "act as a 'critical friend' in their further development".
"Part of the evolution must be to ensure that county cricket is at the game's heart long into the future.
"To see first-class counties reduced to bit-part players will not be an acceptable outcome - no matter how high the profile of the new Twenty20 competition."