While it was clear chemicals had been used, big corporations were manipulating the issue to get control of oil in region, Mr Wellington said.
"I'm not against America ... money dictates today. Money has become evil today."
Mr Key needed to leave the decision with the United Nations and not step in, he said.
"We should stay out of it ... some people want something to happen or to declare war against Syria but I don't think we should. When I heard John Key talking about it on the radio, I was absolutely incensed ... within 15 minutes of hearing him I had that sign up on my fence."
He doesn't shy away from war - in fact he is proud to have fought for his country.
But even Vietnam was a fight New Zealand shouldn't have taken part in, Mr Wellington said.
Vietnam was fought with chemical warfare - Agent Orange.
"It was an adventure as a young man and I'm proud I was a soldier but really annoyed at my ignorance.
"We were all ignorant. Ask anyone who was there ... it's a double-edged sword, really ... it's all about the movers and shakers - big corporations. We need to think for ourselves," he said.
Late last month, Mr Key said he wouldn't rule out the possibility of New Zealand offering military support to any US or British response to chemical attacks carried out by President Basher Al-Assad's regime.
Mr Key said at the time that a UN-sanctioned response was desirable but acknowledged that would be unlikely, considering the Security Council position.
"Our preference is the United Nations, but let's see how things progress," Mr Key said then.