The first two stores are set to open on Thursday in Chatteris, Cambridgeshire, and Immingham at formerly "mothballed" Tesco sites.
Launch of Jack's supermarket in Chatteris.Dave Lewis.
It was reported in July that Tesco was close to launching a chain of discount stores in Britain called Jack's, after Jack Cohen, who founded a business in 1919 that became Tesco.
Bosses of the supermarket giant say the new Jack's store in Fenland Way has created 30 jobs.
Jack's stores will be a mixture of entirely new sites, sites adjacent to existing Tesco stores, and converted Tesco stores.
Lewis, however, said there were no plans beyond the first wave, although it had the option to open more.
The chain is positioned to compete more directly with German supermarket chains Lidl and Aldi, which have increasingly eaten into the profits of larger chains such as Tesco.
Fraser McKevitt, head of retail and consumer insight at Kantar Worldpanel, said: "With its heavy Union Jack branding and promises on provenance Jack's is clearly looking to make its name as a solid British retailer".
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Low pricing, own-brand SKUs and British sourcing appears to be at the heart of Tesco's new offer, with the supermarket committing to sourcing 80% of its food and drink from United Kingdom suppliers.
The shelves will be stocked with an own-brand range, also named Jack's, however stores will also stock some well-known grocery brands and a range of general merchandise.
Tesco now has a 27.4 percent share of Britain's grocery market, according to the latest industry data, although it could be overtaken by Sainsbury's proposed 7.3 billion pound takeover of Asda.
The ceo of Tesco, Dave Lewis, said at the inauguration of the store of Chatteris (central England) that other opportunities were possible, but that "this is not a calculation that we are doing at the present time".
Britain's "big four" grocers are trying to adapt to changing habits, including the declining popularity of big weekly shops and the growth of online shopping.
"Plenty of people buy from Aldi and Lidl - around 60% of all households shop in each of the discounters at least once a year", he said.
He said: "Jack's will need to work hard to dent the success of Aldi and Lidl, and will also need to prove its value against the wider Tesco offering including its existing chain of One Stop convenience stores".