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Average earnings in some parts of Essex have fallen by nearly 15% since the recession.
The figure is higher in some parts of Essex, at more than 14.5% in Southend and 12.4% in Thurrock, according to the GMB union report.
On average across Essex earnings have fallen by 9.8%.
The only part of the UK where the figure has increased since 2008 is Moray in Scotland, according to the report, which compared the increase in average pay with the rise in RPI inflation.
Unions have been warning all year that wages have failed to keep up with inflation, adding that workers were missing out on the upturn in the economy, including an increase in jobs.
Paul Kenny, general secretary of the GMB, said: "These alarming figures show how hard-pressed working people across the UK are struggling to pay their bills after years of wage decline and attacks on the living standards of families throughout the land.
"Working people deserve and need a decent pay rise to halt the drop in living standards.''