MPs on the Business, Innovation and Skills committee have heard a host of objections from trade union representatives to the proposed takeover of Astrazeneca by US drugs giant Pfizer.
Tony Burke of the Unite union, which represents roughly a third of Astrazeneca staff, said his members feared the prospect of job losses.
Both the representatives from the GMB and the Unite union said their stewards were overwhelmingly opposed to the deal.
Burke added that in the past Pfizer had significantly cut back on R&D budgets, while comparable companies had continued to invest at substantial levels.
The GMB's Allan Black said his desired outcome was to see the secretary of state use the powers he has to stop the deal going ahead altogether. However, should the deal go ahead, Black said he wanted firmer guarantees from Pfizer regarding jobs.
Black said he was wrong to call for the deal to be referred to Competition Commission as European competition authorities would examine the deal. He admitted that he did not understand Pfizer's motivation for the deal.
Both the GMB and Unite unions said they had received no official communication from Pfizer. Conservative MP Brian Binley said he was shocked there had been no communication between the unions and Pfizer.
The union officials told the committee they met with the business secretary Vince Cable yesterday.