Shoppers can add extra items to their baskets this Saturday and donate them to Wandsworth's first foodbank.
Giving out food supplies to people in crisis, the foodbank needs to collect three tonnes of food before opening in May.
At Sainsbury's stores in Putney, Balham and Tooting, shoppers will be given a shopping list and asked to buy an item for donation.
At a collection at Waitrose Southside in February, volunteers collected more than a tonne of food and Sainsbury's Putney manager, Jan Willoughby, is hoping for a similar response this weekend.
She said: “We have worked with Trussell Trust Foodbanks previously in other stores, and had such an overwhelming response from our customers to supporting this initiative that we’re excited to be working with Wandsworth Foodbank this weekend.
“We hope we can further raise the awareness of food poverty in the UK and support those families that need our help.”
A neighbouring foodbank in Hammersmith and Fulham is giving away two tonnes of food every month so Wandsworth foodbank manager, Sarah Chapman, wants to make sure they have at least three tonnes in stock before they open.
“Across the UK we're already seeing families with budgets stretched to breaking point and the benefit reforms brought in this week are going to hit them even harder.
“We are expecting to see a rise in the number of people in food poverty. The front-line services that are registering with us across Wandsworth are saying they can't wait for us to open because there is already a high demand.”
For more information about how you can donate to the foodbank, visit wandsworth.foodbank.org.uk.