More than a quarter of the wealth created in Britain over the past 15 years has ended up in the pockets of the richest 1% of people, according to Oxfam.

In a report that singled out “wealthy British tax-dodgers” for withholding funds that could be used to fight poverty, the charity called for a crackdown on tax havens.

It said that the total net wealth of people in the UK had increased from £6tn in 2000 to £10tn in 2015, based on figures from Swiss bank Credit Suisse.

But while just 7p in every pound of wealth created went to the 30 million people who make up the nation’s poorest 50%, around 26p went to the richest 1%.

The 1%, which comprises 600,000 people, increased their collective wealth by 79% to £2.4tn, or an average of £3.7m each, over the 15-year period.

During the same timeframe, the average wealth of someone in the bottom 10%, including debt, rose to £1,600 compared to £1,100, a far more modest 45% rise.

Oxfam said the growth in wealth should be spread more evenly, pointing to figures showing that more people than ever before rely on food banks to feed themselves.

“It’s simply not right that a tiny group of individuals hoovers up so much of the UK’s growing prosperity while barely any trickles down to those who have least,” said Mark Goldring, Oxfam chief executive.

“We need action to ensure that a rise in wealth is more evenly shared in order to combat poverty and ensure everyone gets a fair share.”

In a report titled End the Era of Tax Havens, Oxfam said wealthy people funnelling cash to “secrecy jurisdictions” such as the Cayman Islands and Bermuda were contributing to the wealth divide.

It said the Treasury was losing around £5bn a year from British “tax-dodgers” holding more than £170bn in tax havens.

It also highlighted the impact on the global wealth gap, saying governments are thought to be losing £120bn, with the world’s poorest regions missing out on £43bn.

Oxfam also called on the UK chancellor George Osborne to use this Wednesday’s budget to clamp down on corporate tax-dodging, by requiring UK companies to publish country-by-country data on profits and tax contribution.