In a lengthy statement, the three leagues have called into question the “sporting integrity” of the proposal and expressed their dismay at the lack of “discussion or consideration” for other clubs in the pyramid structure.
The plans would see Celtic and Rangers field a B team in the Lowland League for one season only and they wouldn’t be able to win promotion, an aspect which doesn’t sit well with the other leagues.
Lowland League clubs are set to vote on Monday evening.
The statement in full: "The West of Scotland, East of Scotland and South of Scotland Football Leagues are disappointed and dismayed by the proposal from the Scottish Lowland Football League (SLFL) to invite Rangers and Celtic Colt teams to join their league at tier five of the Scottish football pyramid without any discussion or consideration for clubs in the other leagues within the pyramid structure.
"If this proposal goes ahead, it will have ramifications for clubs from tier five and below, clubs who are ambitious and committed to the Scottish football pyramid and who have worked hard to meet the criteria to allow their club the opportunity to progress through the leagues.
"It is our opinion that there is no sporting integrity with this proposal, nor commitment to the pyramid from the SLFL should they permit the Old Firm Colt teams to join what will become the middle tier of the game, to play a series of friendly matches throughout the season with no prospect of either of the Colt teams gaining promotion or relegation.
"It is our understanding that this pilot is for one season only. But what happens thereafter?
"The three leagues supported the SLFL in its bid to ensure Kelty Hearts had the opportunity to play in the play-offs for a place in the Scottish Professional Football League (SPFL) next season.
"Now they propose a change that could potentially result in the success of the Old Firm Colts denying other clubs that same opportunity.
"It has been stated that the Colt teams could not be promoted next season but no discussion regarding this has taken place with the SPFL.
"Should one of the Colt teams win the league, what guarantee would there be that the second placed club would enter the promotion play-offs?
"The SPFL would be within their rights to deny any runners-up the opportunity to play in the SPFL play-offs as they were not the champion club and as a result, existing Lowland League clubs - plus in future clubs from the other three tier six leagues and below - could be denied the same opportunity that Kelty Hearts have been given this season.
"The three leagues see no benefit in this proposal other than self-interest and a small financial reward for the SLFL clubs but can see a serious risk to the future of the pyramid structure in Scottish football if this is allowed to go ahead, and ask all SLFL clubs to express their commitment to the pyramid by rejecting this proposal."