Disposable incomes in Calderdale and Kirklees just over a quarter of others in the UK
Residents in Calderdale and Kirklees have just over a quarter of the disposable income of people in some other parts of the UK.
The Equality Trust said the figures were "a damning indictment of the glaring inequalities" that exist throughout the country.
The average person in Calderdale and Kirklees had £17,124 left after tax in 2018, the most recent Office for National Statistics data shows.
By contrast, people in Kensington and Chelsea, and Hammersmith and Fulham had more than three times as much – left with £63,286 each.
Calderdale and Kirklees's average gross disposable household income increased by 5% last year, but was still below the UK average of £21,209.
The lowest disposable income in the UK – £13,138 – was in Nottingham.
Dr Wanda Wyporska, executive director at the Equality Trust, said: "The figures are a damning indictment of the glaring inequalities between London and the rest of the country and between north and south, rich and poor.
"This is even more important, as part of the background to the current Covid-19 crisis, which we know has seen higher rates of death in more deprived areas.
"We know that high levels of inequality are accompanied by higher levels of poor mental and physical health, drug and alcohol addiction, violent crime and imprisonment and lower levels of social mobility and educational attainment."
The UK's total gross disposable household income increased by 5% in 2018, to £1,402 billion.
Every region saw an increase in GDHI per head in 2018, but London's remained the highest, at £29,362 on average.
By contrast, Yorkshire and The Humber's was just £17,665 – the ninth highest.
Anna Stevenson, a welfare benefit expert at anti-poverty charity Turn2us, said the economy needs to be rebuilt after the coronavirus crisis to work for everyone.
She said: "At this time, whilst so many people are facing sudden financial turmoil caused by the coronavirus pandemic, these income inequalities will widen even further and cause for grave concern.
“We need to see radical measures that lift left-behind communities within our country out of poverty. These measures should include investment in local infrastructure and jobs as well as increases to wages and benefits - so that families and their community can thrive."
A spokesman for the Treasury said they have injected more than £6.5 billion into the welfare system.
He said: “Our unprecedented package of support will help ensure we continue to support people across the country as our economy reopens – levelling up the country to create an economy that benefits the whole of the UK will be a crucial part of this.
“We have protected more than 8.7 million jobs across the UK with the Coronavirus Jobs Retention Scheme, seen 2.5 million people apply for our self-employed support scheme, introduced mortgage and tax deferrals and made the welfare safety net more generous and efficient.”