Charities and trade unions have warned of a "rising tide of in-work poverty" across the country, with millions of workers struggling to make ends meet.
The latest figures from the Office for National Statistics reveal 20.5 per cent of jobs in Preston earn less than the real living wage – around 17,000 workers in total.
They are among a pool of more than 6m others across Great Britain "struggling to make ends meet" because their wages are less than they need to cover the basics, according to Frances O'Grady of the Trades Union Congress.
The Real Living Wage, which was £8.75 per hour when the data was compiled but has since been revised to £9, is set by the Living Wage Foundation.
It is higher than the living wage introduced by the Government in 2016, which is the legal minimum employers can pay workers aged 25 and over, and instead calculates the minimum amount a person needs to earn to meet their everyday living costs.
The Living Wage Foundation argues that businesses paying the living wage benefit from more productive and motivated workers.
"If we want to build a modern, dynamic economy, we need to see more businesses step up and join the over 5,000 Living Wage employers committed to pay a fair day’s pay for a hard day’s work," said director Katherine Chapman.
The figures reveal stark variations across the country, with the proportion of workers earning below the living wage ranging from a low of 6.3 per cent in the City of London, to a high of 48.7 per cent in Redbridge, in East London.
Regionally, the East Midlands has the highest proportion of low earners (26.9 per cent) while the South East has the lowest (18.8 per cent).
Across the North West, 24.4 per cent of jobs pay below the Real Living Wage.
Helen Barnard, deputy director of policy at the Joseph Rowntree Foundation, said it was vital to invest in places with low employment and low pay.
She said: “It is totally unacceptable that at a time of record employment we are seeing a rising tide of in-work poverty across the country.
"We need to be more ambitious about improving pay and progression for those at the bottom."
Unite assistant general secretary Steve Turner said: “For too many people, the insecurity of not knowing if they will earn enough to pay the bills and put food on the table is a daily fact of life.
“It is an obscenity that we have 151 billionaires in this country while 4.1m children in working households are living in poverty.
“We need to ban exploitative zero and short hours contracts and build an economy where work is stable, secure and pays a decent wage.”
The data also reveals a significant gender gap among living wage earners in Preston.
Women were more likely to earn below the threshold – 25.1 per cent compared to 15.8 per cent of men.
The difference was even more pronounced across Great Britain, with 27.7 per cent of women and 17.7 per cent of men missing out on the living wage.
Part-time workers are more affected by low pay than those with full-time jobs.
In Preston, 9,000 part-time workers are taking home less than the living wage – 43.8 per cent of the total.
Just 12.7 per cent of full-time workers were paid less than the living wage.
A spokeswoman for the Department of Business, Energy and Industrial Strategy said it was committed to fair pay for workers.
"Last month’s rise in the National Living and Minimum Wage has benefited millions of people, and our minimum wage rates are now among the highest in the world," she continued.
"The Low Pay Commission (LPC), who recommend our minimum and living wage rates, are working to increase the Living Wage to 60 per cent of median earnings by 2020.
"But we want to go even further. Later this year we will confirm a new remit for the LPC for the years after 2020, with the objective of ending low pay in the UK."