The giant Primark warehouse near Islip is due to come into operation next summer, employing 300 people.
Many of those posts could be filled by workers currently employed at the budget fashion store’s centre 35 miles away in Lutterworth, which is closing next year.
The Unite union, in discussions with Primark, said workers would be given the oportunity to move if they wanted to.
A statement from Primark said: “We have entered into a lease agreement with London Metric Property to develop a new distribution centre to support continued business growth.
“This will be a one million square foot facility located at Islip.
“This facility will come on stream in 2016 and as a result of this, the Magna Park distribution centre, Lutterworth, which is currently managed by Ceva, regrettably will cease operations.
“Primark expects this transfer of operations from Magna Park to Islip to take place by the middle of next year with a view to ceasing activity at Magna Park by September 2016.
“The distribution centre in Thrapston will continue to operate in conjunction with the new Islip depot.
“The decision to move operations from Magna Park to Islip has been a very difficult one and follows a lengthy and detailed review of all options aimed at increasing capacity.
“Ultimately, transferring to the new, larger depot configuration at Islip will provide Primark with essential capacity and flexibility for growth.
“We are exploring alternatives for those affected at Magna Park, including transfer options to Islip. A full consultation process is currently under way.
“All those involved will be kept regularly up-to-date as discussions progress.
“Primark will do its upmost to support everyone through this process.
“Primark sincerely thanks all colleagues at Magna Park for providing excellent support and for their continued commitment to on-going operations.”
The Primark move is bad news for Magna Park owners IDI Gazeley, who would have hoped to retain such a big client at their Lutterworth hub.
The cash and carry group Costco also moved out of Magna Park recently.
IDI Gazeley Planning Director Gwyn Stubbings said: “We like to think if we could expand Magna Park, and new space was available, then most growing businesses would seriously consider staying here.”