The rich are mostly to blame for the climate crisis, according to researchers who found that the more money people have, the greater their energy footprint.

The wealthiest tenth use up about 20 times more overall energy than the bottom 10 percent, wherever they live, according to a new study published in the journal Nature Energy.

Researchers from the University of Leeds said that, among 86 countries and income classes studied, energy footprints grow with expenditure and, as a consequence, are unequally distributed.

The study combined European Union and World Bank data to calculate what energy-intensive goods and services different income groups tend to spend their money on.

The gap is greatest in transport, where the top tenth consume 187 times more fuel than the poorest tenth, because people on the lowest incomes can rarely afford to drive.

The top 10 percent of consumers used more than half of the total energy related to travel, with the majority of it based on fossil fuel.

Residential fuels, such as those used in cooking and heating, and electricity are much more equitably distributed, with the top 10 percent consuming roughly one third of the total.

Unless there is a significant policy change, researchers warn, household energy consumption could double from 2011 levels by 2050, even if energy efficiency improves.

According to a leader of the project, Julia Steinberger, "richer households, around the world, tend to spend their extra money on energy-intensive products", such as package holidays and fuel for their cars. Spending on transport－land, air and water－was one of the most important factors in this difference, she said.

Co-author Yannick Oswald said: "We found that none of the energy categories are free from energy inequality or benefit populations to an equal degree.

"Transport-related consumption categories are among the least equal. Without reducing the energy demand of these services, either through frequent-flyer levies, promoting public transport and limiting private vehicle use, or alternative technology such as electric vehicles, the study suggests that as incomes and wealth improve, our fossil fuel consumption in transport will skyrocket."

In terms of solutions, the authors say governments could reduce transport demand through better public transport, higher taxes on bigger vehicles and frequent-flyer levies for people who take the most holidays.

They say another alternative is to electrify vehicles more quickly, although previous studies suggest even then demand for driving must be reduced in order to reduce the strain on resource use and electricity production and distribution.