A 20-strong consortium covering Bristol, Cornwall, Devon, Dorset, Gloucestershire, Somerset and Wiltshire has been accused of undermining national standards by plotting their own, lower regional deal.
Unions have warned that the plan will result in a brain drain as the highest skilled workers seek higher pay elsewhere.
They also say that lower pay will have a direct impact on the local economy.
And the Unite union said yesterday that managers at the trusts have resorted to bully-boy tactics to silence criticism from its reps.
The union's head of health Rachael Maskell said: "We have evidence that up to a dozen Unite reps have been threatened in their roles as legitimate trade union representatives.
"They have been threatened with disciplinary action and told they can't speak to staff about the proposed changes, and refused permission to distribute leaflets and other information material.
"This intimidation must stop."