While many regions have seen earnings tumble since the recession five years ago, Moray is the only area of the country to buck the trend.
According to the GMB union, earnings have fallen by almost 14% since the recession five years ago.
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 the capital, the value of average pay has slumped by almost 50%, said the GMB union 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, with the top four in London. In Hammersmith and Fulham, they were down 49%. In Camden , they fell 30% and in Haringey 26%. Earnings in Greenwich fell 24%.
Warrington residents saw earnings drop 24% while they fell 23% in Sheffield, Windsor and Maidenhead and Harrow.
Other areas with above-average falls included Blackpool, Hartlepool and Portsmouth (22%), and Swindon, the Scottish Borders and Walsall (20%).