Hearts and Partick Thistle have lodged legal papers calling on the Scottish Professional Football League to reverse the decision to relegate them at the end of last season.
The clubs call the relegations – the result of a vote of SPFL member clubs which ended the 2019/20 season early due to the Coronavirus crisis – “unfair and unjust” and describe the effects “to the extreme detriment of those clubs affected”.
The petition to the Court of Session demands financial compensation only if the clubs fail in their bid to be re-entered in the Premiership and Championship respectively.
The clubs have not asked to place an interim interdict preventing the start of the Scottish Premiership season – but they do not rule out such a move “in the event that becomes necessary”.
A joint statement from the Edinburgh and Glasgow sides said: “Unfortunately, Scottish football has been unable to pull together at this time of national crisis to prevent the need for this legal challenge.
“We desperately hoped court action would not be necessary, but we were left with no other option.”
Hearts were sent to the Scottish Championship as they sat bottom of the Premiership by four points with nine games to play.
Thistle were just two points behind Queen of the South with a game in hand, at the foot of the second tier when the season was declared over.
Stranraer were also demoted from League One.
The court granted Hearts and Partick Thistle’s motion requiring the SPFL to respond within seven days.
A spokesman for the SPFL said: “Our solicitors have received a petition from Heart of Midlothian PLC and The Partick Thistle Football Club Limited.
“We are studying this carefully, along with our legal advisers, and it is not therefore appropriate to comment further at this time.”