Over 200 representatives from 130 organisations met at the summit today to discuss the plans announced by the new UK energy minister, Amber Rudd, last month.
Scottish Renewables senior policy manager Joss Blamire said the decision by the UK government was irrational and illogical: "There's a huge lack of clarity from the UK government. Fundamentally, Scottish Renewables opposes the decision to close the RO a year early. It is a retrospective decision and a lot of people have put in a lot of investment in good faith, which could potentially now be lost.
"Not only that it seems irrational. The Conservatives' manifesto pledge is to try to combat climate change at the lowest possible cost and that is exactly what onshore wind can deliver," he added.
Scottish Renewables believes approximately £3 billion (€4.1 billion) of investment is being put at risk because of the announcement.
Blamire also criticised the UK government for creating uncertainty with the legislation. Under the new law, RO would be closed to new entrants from April 2016, a year earlier than originally planned.
Blamire said because the government is trying to implement the changes through primary legislation, it may be spring 2016 before the law is finalised, possibly just weeks before the change comes in to effect. "That's obviously holding up investment and creating a huge amount of uncertainty," he said.
The UK government's policy was "anti-business", said Ewing. "The impacts could spread right across Scotland and the wider supply chain, including ports and harbours, transmission and distribution, consultancy, commnities and the civil engineering sector," he said.
The Civil Engineering Contractors Association in Scotland said the closure of the scheme could put up to 3,000 jobs at risk. Scottish Renewables said there were 5,400 jobs in the onshore wind sector in Scotland.
Ewing had threatened to pursue a judicial review into the subsidy closing. Blamire said the trade body was taking legal advice on the change.