All 12 top-flight clubs met at Hampden on Tuesday to discuss plans for league reconstruction amid other radical reforms including an earlier start to the season, a winter break and the re-introduction of play-offs. Afterwards SPL chairman Ralph Topping and chief executive Neil Doncaster claimed to be optimistic the plan to have an SPL 1 and 2 with 10 teams in each division would be ratified at the next meeting on January 17.
An 11-1 vote is required to push the proposal through, but Thompson, who reportedly could have the backing of three other clubs, said: "We will certainly be voting against it if it's the same proposal as before - and I'd imagine we won't be the only ones."
He added: "I wasn't at the meeting so it is difficult to gauge the mood and how argumentative it was.
"But the bottom line for me is that I don't think a 10-team league is good for Scottish football.
"It will stifle youth football and put all eight non-Old Firm clubs in danger of relegation.
"I don't think it will do much for the entertainment value because it will bring a fear factor in to most games.
"Some teams could end up playing to avoid relegation from the very first day of the season and that will encourage negative football."
Topping claimed a two-tier SPL was the only viable way for the game to survive and he was backed by Aberdeen chairman Stewart Milne and his St Johnstone counterpart Geoff Brown.
However, Thompson's comments have cast fresh uncertainty over the controversial proposals.