Miserly employers are paying Brummies half the wages that workers get in other parts of the country for doing the same jobs.
Staff can now check their pay packet against others across the country on the new Pay Wizard website.
Union chiefs today blamed the pay disparity for a "brain drain" from the West Midlands to better paid areas like London.
TUC regional policy and campaign manager Alan Weaver said: "I believe the West Midlands is a great place to live, but that doesn't put bread on the table."
Shocking statistics show electroplaters are paid an average gross wage of £6.77 an hour in the West Midlands, compared to £13.60 an hour in Wales.