London-based West Six and North One Garden Centres have stopped selling weedkiller Roundup after pressure from customers.
The decision will see them become two of the first retailers in the UK to follow several European retailers that have withdrawn glyphosate-based products.
Owner Beryl Henderson said customers' concerns about reported health risks associated with the active ingredient glyphosate had led to both the garden centres taking the product off their shelves in June.
North One local authority Hackney Council has come under pressure to ban herbicides, from a group using petition website 38 Degrees to lobby for action.
It stated: "The Hackney mayor (Jules Pipe) also claims that there is no point banning the council from using Roundup if it is still available in garden centres. We plan to lobby local retailers and ask them to stop selling Roundup."
It continued: "PAN UK, starting with Brighton and Hove, wants to see a radical shift in thinking about pesticide use in towns and cities across the UK with the ultimate goal of the complete cessation of their use."
The campaign has the support of local groups including Brighton Breast Cancer Action and the Brighton & Hove Organic Garden Group. PAN UK said local campaigns are also emerging in Falmouth, Camden and Newcastle, as well as Hackney.
Glyphosate was classified as "probably carcinogenic" in March by the International Agency for Research on Cancer (IARC), the World Health Organization's specialist cancer agency.
Monsanto business director Gary Philpotts said: "Glyphosate's regulatory status is perfectly clear and as of today there is no new or recent scientific data that has given regulators pause to question its authorisation or sales conditions. Monsanto and other producers of glyphosate-branded products continue to work with the competent regulatory authorities to ensure the 10-year European renewal for glyphosate. Glyphosate was last renewed for sale within the EU in 2003.
"Monsanto is confident in the quality of the products that we offer to gardeners and which have been specifically designed for a safe usage at home. When used according to the recommendations on the packaging, the product does not pose any specific risks to the user."
Meanwhile, the IARC has evaluated the carcinogenicity of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) as "possibly" carcinogenic to humans. The product is in domestic lawn weedkillers made by Scotts, Westland, Bayer and others. It has been defended by manufacturers, who insist it is safe to use.
Philpotts, who is also chairman of the Common Sense Gardening Group, said: "It's important to note that 2,4-D is amongst the most thoroughly tested and evaluated herbicide products on the market. Numerous health assessments conducted by public authorities over 70 years have consistently concluded that 2,4-D does not pose an unacceptable risk to public health."
He added: "Human health and responsible use of garden-care chemicals is and must always be our highest priority. As an industry we take pride in the detailed submissions we provide to regulators and the extreme rigor with which our products are assessed. Gardeners and the general public should rest assured that these products are safe and effective when used according to the instructions on the label."
Roundup Gel Sales
The popularity of Roundup Gel continues to rise in the UK, with unit sales up by 31 per cent versus the same period last year (GfK Panelmarket Hitlist January to May).
The overall market is down 1.4 per cent in units and down 4.9 per cent in value.