Shelter Scotland argued that giving local authority and housing association tenants a longer notice period could be "potentially damaging" for more vulnerable people.
The Housing (Scotland) Bill includes provisions to abolish the right-to-buy policy which was first introduced in the 1980s and gives eligible tenants the opportunity to purchase their home at a discounted price.
The move has been welcomed by Shelter Scotland and housing associations, who argue the scheme has led to a reduction in social housing stock, and contributed to waiting lists.
But the organisations do not support the Scottish Government's plans to give a three-year notice period.
Appearing at Holyrood's Infrastructure and Capital Investment Committee, Shelter Scotland policy manager Rosemary Brotchie said a period of six months to a year might be more appropriate.
She said: "I think the period of notice which is given is excessive, I don't think it's necessary and could potentially be quite damaging.
"We also know that when the right-to-buy has been restricted or limited there are companies out there who act, and who prey upon almost, vulnerable tenants to persuade them to purchase their properties, and actually it may not be the right thing for them to do, financially or in terms of their security."
Ms Brotchie said there were cases where tenants were approached by companies offering to secure a mortgage for them, or purchase the home and then rent it back to them.
Alan Benson, director, Glasgow and West of Scotland Forum of Housing Associations, and Andy Young, policy manager, Scottish Federation of Housing Associations, agreed that a year-long notice period was "more appropriate".
David Bookbinder, head of policy and public affairs, Chartered Institute of Housing in Scotland, suggested a two-year period would still give tenants adequate time to consider whether to purchase.
Committee convenor Maureen Watt asked if a shorter period of notice would cause a "rush of tenants" wanting to buy.
Mr Young told the committee: "We really just don't know. There always is a danger that if you make it a year there might be a stampede, but in reality I can't see that happening."
Earlier, Mr Bookbinder told the committee that scrapping the scheme would be of "huge benefit" to councils and housing associations.
He said: "The longer-term argument is a no-brainer - that supply is increased."