The Transport & General Workers' Union (T&G) was locked in talks with bosses at the HP Sauce plant in Aston Cross as Food Manufacture went to press in a last-ditch attempt to persuade Heinz to reconsider closure.
Heinz said that transferring production to Elst in the Netherlands would save £15M over 10 years, but the T&G claimed that cash might be available from the development agency Advantage West Midlands (AWM) and Birmingham City Council to secure the 125 jobs.
John Jordan, national secretary at T&G's food and drink division, said he also wanted to see if savings could be generated through new working practices.
"Aston Cross is profitable and modern. Danone [HP's former owner] had invested in the site, which is heavily automated, so it's not a case of being old or inefficient," he said.
"It will be an outrage if they continue to use the picture of the Houses of Parliament on HP bottles when they are made in Holland," added Jordan, who said a protest rally would be held on June 3. "We'll start at Aston Park and walk to the factory."
Heinz said it had met Department of Trade and Industry officials, the city council and AWM as part of the consultation process, but rejected claims by the T&G that it had given workers any assurances about job security when it took over last year.
Meanwhile, an early day motion tabled by Birmingham Perry Barr MP Khalid Mahmood, calling on Heinz to change its plans, has been signed by more than 120 MPs. It reads: "This House is concerned at the loss of employment that this move will cause in an area which already has high unemployment ... and is further concerned that this factory will be closed without further consultation."
If the closure goes ahead, production will begin transferring to Elst in November, with the site winding up next March. Lea & Perrins Worcestershire Sauce bottling would be transferred to HP's factory site in Worcester.