Last month, the SPL agreed to seek the expansion of their membership, with plans that would see two leagues of 12 split into three divisions of eight after 22 games, with 18 teams left in the SFL.
"I'm delighted to say that we have unanimous agreement in principle from the 12 SPL member clubs to the 24-18 team model," he said.
"We are looking forward to sitting down with the Scottish Football League and the Scottish FA to talk about the details."
Doncaster gave a strong hint that some top-flight clubs were willing to share more wealth with the lower leagues, but was reluctant to discuss whether they would want any new format to fall under the umbrella of the SPL.
"We understand that there needs to be a lot of redistribution from the biggest clubs and that's something which the clubs, in principle, bought into," he said.
"We need to sit down with the other clubs and the SFA and agree the best way forward for everyone."
The SFA have been attempting to drive both leagues towards consensus and president Campbell Ogilvie believes that is possible despite the SFL clubs last month unanimously backing significantly different plans for a 16-10-16 structure.
"There is a lot of common ground between the two league bodies," Ogilvie said today. "So often the debate is centred around the number of teams in leagues. That's not the answer."