Australian Ben Garuccio's Hearts will start legal action against their relegation after the Scottish Professional Football League said that not enough clubs had voted for a league reconstruction and a 14-team Premiership from next season.
Only 16 of the 42 clubs supported an expanded Scottish top-flight, leaving the SPFL to "draw a line" under reconstruction talks.
"The SPFL Board today announced that a league-wide consultation exercise has shown there is insufficient support for a new divisional structure and that the current 12-10-10-10 format will remain in place for season 2020/21," the SPFL said in a statement.
Hearts, who were bottom when the season was ended due to the COVID-19 crisis, said they were "disappointed, yet sadly not surprised" by the decision.
"Now that all other avenues are closed, we are left with no choice but to proceed with a legal challenge," Hearts said in a statement
"The club has tried throughout these last few months to avoid this course of action but we must now do the right thing by our supporters, our employees, our players and our sponsors.
"To our amazing fans we say that we cannot, and will not, sit idly by and watch the decisions made in the past few months further damage the club."
The end of reconstruction talks also confirmed Partick Thistle have been relegated to League One and Stranraer to League Two.