Millions of workers are being given the chance to compare their pay and pensions with those of their bosses.
People will be able to search for the information online
The figures for 7,000 UK firms will be shown on the TUC's WorkSMART website, alongside information about shareholders and staff representation.
It says detailed information that is normally buried in annual reports will be clearly revealed for the first time.
TUC assistant general secretary Kay Carberry said it would let prospective employees "check out" companies.
"Most employees in the country will now have freedom to get important information about their company with the click of a mouse rather than digging through reports," she said.
"Company finder also enables job seekers to check out a firm before interviews or accepting a post.
"The TUC will continue adding to this search tool to give current and prospective employees as much information about UK plc as possible."
The search is available at www.workSMART.org.uk/company.
But Steven Bevan from the Work Foundation - a think-tank on employment issues - said he foresaw problems: "You need a positive, trusting culture in an organisation for everyone to be happy for their pay to be transparent.
"Back in the 1960s, lots of men didn't tell their wives what they earned. This mind-your-own-business' aspect is still pretty pervading."