Davies said it was “not the sort of politics” he wanted to be associated with, and that Green Party Wales leader Slaughter had been supportive of his decision to leave the party.
He said: “Our views are exactly the same to be honest with you.
“He sent me a very nice message yesterday as well. I class Anthony as a close friend and that will remain.”
When asked on whether Slaughter would follow him in quitting the party, Davies said he did not agree with any elected official resigning and staying in the Senedd.
“You weren’t voted in as an individual member under this system. You’re voted in under your party banner,” he added.
He suggested that Welsh members of the party should consider splitting from the Green Party of England and Wales (GPEW) to “stand on our own two feet as a Welsh party” in light of the motion.
Davies said he was “hoping they’ll vote to leave” at their party conference next month.
In an Instagram post, Davies said he had not been treated with respect or been “given enough support from the GPEW”.
He added: “I have often felt like the token Welshman moaning at various points, but have not seen enough action taken by GPEW.
“I also feel the position of Wales deputy leaders is ignored rather than supported by GPEW.”
Anthony Slaughter, who revealed he had been diagnosed with cancer last month, said his former colleague had brought a “much needed new perspective to Welsh politics.”
He said: “I am positive he will contribute a great deal to Welsh public life whatever his next steps are.
“While the recent motion is not the only reason for Phil’s resignation, I know it has stirred emotions across our party as people express their positions on this issue.”
First Minister Rhun ap Iorwerth said on Tuesday that the Green Party policy was “ill-judged”, saying that he had always advocated the two-state solution.
He had been responding to Reform Wales leader Helen Jenner, who had accused “left-wing parties” of having a “sickening antisemitism problem”.
Speaking in the Senedd on Tuesday, ap Iorwerth said he always advocated the two-state solution and stood “shoulder to shoulder with the Jewish communities in Wales”.
Additional reporting by David Deans.
