The real value of average earnings has fallen by almost 14% since the recession five years ago, an "alarming" new study has shown.
The figure is higher in some parts of the UK, at more than 20% in London and 15% in Yorkshire and the Humber, according to the study.
In some parts of London, the value of average pay has slumped by almost 50%, said the GMB union report.
The only part of the UK where the figure has increased since 2008 is Moray in Scotland, said 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."
The GMB's study, based on official data, listed the worst areas in the UK for the drop in average earnings:
:: Hammersmith and Fulham in London (down 49%).
:: Camden in London (30%).
:: Haringey in London (26%).
:: Greenwich (24%).
:: Warrington (24%)
:: Sheffield (23%).
:: Windsor and Maidenhead (23%)
:: Harrow in London (23%).
Other areas with above-average falls included Blackpool, Hartlepool and Portsmouth (all 22%), and Swindon, the Scottish Borders and Walsall (all 20%).