Councillors have raised concerns about the transfer of mail processing in Hull to Sheffield 70 miles away.
Coun Steve Bayes is calling on Hull Council to start a campaign to keep processing at the Malmo Road sorting office.
He fears collection times will have to be brought forward to allow mail to be taken to Sheffield and then brought back to Hull to meet schedules, with a knock-on for businesses.
His motion to full council next Thursday asks for a letter to be sent to the Royal Mail asking them to keep the processing of mail in the city.
However, Royal Mail said the changes, first announced last November, were necessary.
Spokeswomen Marie Gray said: “Following more than five months of consultation with our unions and careful evaluation of a range of options, Royal Mail established that it can operate most effectively with a regional network of three mail centres in Tyneside, Leeds and Sheffield.
“As part of these changes, processing work from Hull Mail Centre will transfer to an extended Sheffield Mail Centre whilst delivery and collection operations will remain at the current site on Malmo Road. Hull Mail Centre is expected to remain open until 2015.
“With people demonstrating reasonable flexibility, Royal Mail expects that everyone who wants to remain in the business will be able to do so. Furthermore, the majority of people who currently work at Malmo Road will continue to be employed at the site.”
Because of the huge increase in electronic mail, the group says 16 million fewer letters are being posted every day, compared with five years ago, and rivals now carry more than one in three letters and more than half of all business mail. While they still delivered letters, much of the collection and regional processing work was done by competitors.
It said the changes were “necessary to protect the long term future of the business and ensure a sound, secure and sustainable Royal Mail”.