A union protested outside May Gurney's Norwich offices today over a blacklisting scandal linked to the firm which is poised to buy them.
Around 20 members of Unite were outside May Gurney's Trowse base, waving banners and flags and playing music in front of a giant, inflatable rat.
Unite said it wanted to warn May Gurney's workers about construction firm Kier who are set to buy them in a takeover deal.
Unite claims Kier was involved in the blacklisting of employees who were trade union members and raised concerns about health and safety.
Kier said the allegations were 'historic' and it complied with an investigation by the Information Commissioner's Officer in 2009 into blacklisting.
But Unite said the practice was continuing.
They claim 28 workers were made redundant by sub-contractor EIS in September 2012 because of the scandal.
EIS were working for a consortium which included Kier on the London Crossrail project.
Frank Morris, a Unite shop steward who was working on the project, said he was banned from the site for raising concerns about cabling.
The 38-year-old has not worked since last September and says he is struggling to get a job since allegedly being blacklisted.
'It affects your entire life,' he said. 'You are in danger of losing your home and you cannot function.'
Unite warned May Gurney yesterday that their members would continue to hold protests at their offices.
Erkan Ersoy, from Unite, said: 'We will continue to protest against May Gurney. They are putting their reputation at risk.'
A spokesman for Kier said: 'The activities of the now disbanded Consulting Association are both historic and clearly regrettable.
'Kier co-operated fully with the investigation by the Information Commissioner's Office in 2009, when no action was taken.
'Kier does not condone any form of blacklisting.'
A spokesman for May Gurney said: 'Blacklisting is something that May Gurney has never practised or supported.
'Our employment policies are based solely on performance and merit. We always seek to not only comply with legislation, but to build a working environment that is visibly free from discrimination or victimisation of any sort.'
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