Thousands of workers at Morrisons supermarket depots are to stage nine days of strikes in a row over jobs.
Workers at five Morrisons depots have voted to strike
Members of the Transport and General Workers Union (TGWU) at depots in Bristol, Wakefield and Northwich will begin walkouts from 23 September.
The GMB's members at Aylesford in Kent and Warrington, Cheshire are expected to join them after 60% voted to strike.
A spokesman for Morrisons said it would be discussing the outcome of the two strike ballots with the unions.
The result of the GMB ballot was announced on Thursday, a day after the TGWU said its members would walk out.
Three days of strikes are planned from 23 September, then six days from 29 September. The unions will also ban overtime.
Paul Kenny, acting general secretary of the GMB, said: "This is a clear message from the workforce to the management to listen to them and be honest about the future."
Mr Kenny called on the company to do some "straight talking" about any plans to cut jobs if strike action was to be averted.
The unions believe Morrisons is planning to close three distribution centres - Aylesford, Bristol and Warrington - with the potential loss of 2,500 jobs.
The depots were acquired with Morrisons' takeover of Safeway in 2003.
Store for sale
The company has said it had made it clear a "thorough review" of its depots was under way but it was unlikely all of them would remain open.
The TGWU has warned strike action raises the prospect of "serious shortages" on Morrisons shelves but the company pointed out it had 12 other distribution sites which are not involved in the strikes.
"We will continue to ensure that our stores continue to be well served and our customers are able to shop normally," it said in a statement.
A spokesman said the company had a great deal of flexibility in drawing up contingency plans.
In a separate development on Thursday, Morrisons announced it was putting its store in Tunbridge Wells, Kent, on the market.
The decision to sell the former Safeway site was part of the review of the long-term future shape of the company.
"This is the first stage in the process and unfortunately we are unable to estimate the time period involved in finding a purchaser," it said.
"The store will, in the meantime, trade as usual."