TORONTO - About $5 billion in potential investment could go elsewhere if Ontario bans solar panels from prime agricultural lands, the Canadian Solar Industries Association warned Tuesday.

The government refused to confirm that it will ban solar panels from class A1, A2 and A3 farmlands when it announces regulations later this week for its Green Energy Act, but that's what the industry is hearing, said association president Elizabeth McDonald.

The problem with a ban, said McDonald, is those farmlands also tend to be the ones that get the most sunshine, and they often provide easy access to the electricity grid.

"This agricultural land tends to be close to the transmission lines and, yes, sun is important for agriculture as well as for solar," McDonald said in an interview.

"All we've said we need is .11 per cent of the agricultural land in Ontario, and much of this land isn't being used right now (for farming)."

That works out to about 20,000 acres (81 square kilometres) of land, some of which is already used for alternative energy production such as growing corn for ethanol, said McDonald.

Premier Dalton McGuinty refused to confirm the new restrictions on solar farm projects Tuesday, but said the government had "worked really hard" to strike the right balance as it develops a new green sector of the economy and creates new jobs.

"We're going to do a much better job of harnessing energy from the sun and biomass (and) at the same time not compromise quality of life or the environment and not compromise our access to good farmland as well," McGuinty said at the International Plowing Match in Earlton, a community in northern Ontario.

The New Democrats said the Liberal government should make it easier for companies to start green energy projects, not harder.

"Certainly nobody wants to see good agricultural land itself be lost to other kinds of activity," said NDP Leader Andrea Horwath.

"However, if there's opportunity for farm families to engage in green energy projects we should be doing everything we can to make that happen."

Imposing a ban on prime agricultural lands could scuttle large-scale solar farms projects in Ontario, which McDonald said have the potential to create 10,000 long-term jobs, and in the process, help train local workers for the green economy.

"You take a lot of people and teach them how to mount panels, etc., and then often . . . these are the people who become the local installers in the town or cities," she said, citing the experience with solar farms in several European countries.

"(A ban) is going to limit growth and with that goes the jobs and manufacturing potential, etc."

Solar panels also provide rental income to farmers, and the companies have plans to decommission the solar farms after 20 years and return the land for agricultural use, said McDonald.

"We're very willing to do whatever studies that might be requested when we go into areas," she said.

The Liberal government will unveil the regulations to support its highly touted Green Energy Act later this week, which will also include such things as mandatory set-backs from residential areas for industrial wind turbines.

Solar power companies have been anxiously waiting for the regulations, which could be the deciding factor for whether or not new solar farm projects get off the ground in Ontario or move to the growing U.S. market for alternative energy supplies, said McDonald.

"Companies are sitting here trying to make up their minds," she said.

"The competition is increasing and companies will be saying `is there enough of a market to stay in Ontario or are we going to go elsewhere where it might be less onerous?"'

A spokeswoman for Energy Minister George Smitherman wouldn't comment Tuesday on the potential ban on solar panels, and said any such restrictions would be announced as part of the regulations for the Green Energy Act.