The effect of rising inflation means workers earned less in real terms in 2017 than they did 10 years earlier.
Research by the GMB general union found the average salary for a full-time worker in the UK increased from £30,015 in 2007 to £35,423 a decade later.
However, the effect of inflation means that workers are poorer in real terms.
By the time total inflation of 31.7% over that period is factored in, full time workers have received a real term wage cut of 10.4%.
The union is calling on firms to increase their employees’ wages to ensure they are not left poorer than they were a decade ago.
The situation is particularly acute in London, where the average salary has increased from £42,226 to £47,089 in the last 10 years.
Yet once inflation is factored in, this represents a fall in earnings equivalent to 15.4% in real terms. This is seen most markedly in the London borough of Hillingdon, where wages in 2017 were just 75.2% of what they were in 2007.
Warren Kenny, GMB regional secretary for London, says: "Across London as a whole, the real value of average wages for workers resident in the region in 2017 are only 84.6% of the buying power they had in 2007 when inflation is factored in as this latest study by GMB shows.
"Two conclusions can be drawn from the study. The first is that the impact on the living standards of ordinary workers of the bankers’ recession in 2008 onwards is still with us a decade later.
"The second conclusion is that ordinary workers require substantial pay increases to make up the lost ground. These increases are needed to boost spending power to keep economic growth on track."
According to the Office for National Statistics (ONS), the consumer prices index (CPI) rate of inflation was 3.1% in the year to November 2017 – the latest figures available. This is well above the Bank of England’s 2% target.
The next inflation data will be released by the ONS on Tuesday 16 January.