Highly paid employees in Burnley earn about £21,000 a year more than those on the bottom rungs of the salary ladder, figures reveal.
The Equality Trust says figures from the Office for National Statistics, which reveal a gap of nearly £25,000 between the UK's highest and lowest earners, "paint a depressing picture of dangerous income inequality".
In Burnley, the average weekly pay packet for the top 20% of earners in full-time roles is now 2.2 times those in the bottom fifth – a gap of £21,278.
The figures, for workers who live in the area, use median, rather than mean, averages, to stop them being skewed by particularly small or large salaries.
They show the top 20% of earners were paid £755 weekly on average, or £39,270 annually.
For low earners, weekly pay was just £346 – £17,992 a year.
The average full-time employee in Burnley works 37.5 hours per week, with a median annual salary of £24,086.
The figures refer to basic pay and do not include bonuses or overtime.
The pay gap between Burnley's highest and lowest earners is in line with the UK average.
Across the UK, the average annual salary for the top 20% of earners is 2.2 times as high than the lowest earners.
Top earners are paid £44,533 on average, compared to £19,874 for their lowest-paid counterparts.
London had the greatest gap, where top-paid earners took home £56,300 – nearly £33,000 more than low earners.
Most equal was Wales, where the highest 20% of earners were paid 2.1 times that of the lowest fifth.
Dr Wanda Wyporska, executive director of charity the Equality Trust, said: "Just like the gender pay gap, the gap between high and low paid workers is not shrinking fast enough.
"But this is an even greater scandal because the evidence shows that in countries with high levels of inequality, like the UK, there are higher levels of violent crime, physical and mental ill-health, infant mortality and lower levels of trust and educational attainment.
"By continuing to ignore inequality, decision makers are failing to truly realise the social and economic potential of this country."
The Trades Union Congress estimates one in nine UK workers are in insecure and poorly paid "precarious work", including those on zero-hours contracts and self-employed people making less than the minimum wage.
General secretary Frances O'Grady said: "Working people deserve a fairer share of the wealth they create. It's not right that millions are struggling to make ends meet, while those at the top pocket bumper pay cheques.
"We need to reset the balance of power in our economy.
"That means giving workers new rights so they can access the protection of a union in every workplace and bargain for better pay and conditions across industries."