These branches are in Lewes High Street and Uckfield.
The 43 closures follow 32 that were previously announced in February, which included 11 of its Royal Bank of Scotland branches.
Government High Streets Task Force expert and ShopAppy founder Dr Jackie Mulligan said: “This is such disappointing news from a bank that has always been part of the UK’s high streets and has championed the small businesses that trade on them. Their ‘Tomorrow Begins Today’ advertising slogan feels a little bit redundant now. For most small businesses in town centres, this will put a lot more uncertainty into their tomorrows.
“Banks provide services and employment in communities, which drives footfall and custom to our much loved high streets across the country. Tomorrow for NatWest feels like a virtual one now and that will be a blow to many small high street businesses at a time when they least need more uncertainty.”
In pictures: police and ambulance close road in Bognor Regis after reports of cr…
A NatWest spokesperson said: “As with many industries, most of our customers are shifting to mobile and online banking because it is faster and easier for people to manage their financial lives. We understand and recognise that digital solutions aren’t right for everyone or every situation, and that when we close branches we have to make sure that no-one is left behind. We take our responsibility seriously to support the people who face challenges in moving online, so we are investing to provide them with support and alternatives that work for them.”
NatWest said it would contact its vulnerable customers to offer them support and make sure they are not ‘left behind’.
According to National World, NatWest said average counter transactions had shrunk by nearly two-thirds between January 2019 and January 2022, while it saw a 39 per cent rise in customers using mobile apps during this same period.