A boost from an above-inflation increase in the “national living wage” has reduced the percentage of people classified as low paid in Britain to its lowest level since modern records began.

A 4.4% jump in the low-pay floor to £7.83 an hour in April 2018 contributed to a jump in average weekly earnings of 2.9% in the subsequent 12 months, the Office for National Statistics (ONS) said.

But despite the above-inflation rise in median wages, the annual survey for hours and earnings shows that workers are still clawing back the ground lost when pay was cut and frozen during the deep recession of 2008-09.

The ONS said that when adjusted for inflation median pay was up by 0.9% on the year to April 2019 but still 2.9% – or £18 a week – lower than it was in 2008.

The ONS senior statistician Roger Smith said: “Earnings continued to increase in the latest year. In recent years this has been fastest among the lowest-paid occupations. However, taking inflation into account, real pay is still some way below its pre-crisis level.”

Tackling low pay looks set to play a big role in the next general election, with Labour pledged to an immediate increase in the minimum wage to £10 an hour for all workers over 18 and the Conservatives promising a rise to £10.50 over the next five years.

The ONS said that the proportion of low-paid employees – those on less than two-thirds of median hourly earnings – stood at 16.2%, the lowest since the survey series began in 1997.

London had the smallest percentage of low-paid employees, while Northern Ireland, the east Midlands and the north-east had the highest.

The highest-paid full-time jobs were paid almost five times as much an hour as the lowest paid, though the gap has narrowed in the past five years as a result of a series of above-inflation minimum wage increases.

The ONS said that in the year to April 2019 hourly pay for the top-paid 5% of workers increased by 1.8% – slightly less than the 1.9% median – while hourly wages rose by more than 4% for the lowest paid 30%.

Frances O’Grady, the TUC general secretary, said: “Pay packets are still worth less than 11 years ago. That’s not right. The Conservatives have presided over the worst wage squeeze since Napoleonic times. Years of austerity and inaction have deepened Britain’s cost of living crisis. It’s about time politicians deliver for working families and get wages rising.”

The Institute for Fiscal Studies thinktank said some groups had fared better than others over the past 11 years. Men, especially those with low weekly pay, people in their 30s, and Londoners had been affected by a bigger fall in their real pay than the median, but women – most affected by the rising minimum wage – were better off than in 2008.

Nye Cominetti, an economic analyst at the Resolution Foundation, said pay growth for the typical worker had returned to pre-financial crisis norms but that this followed a “disastrous” decade.

“Pay growth for the typical worker in Britain returned close to pre-crisis norms over the past year, but this follows a disastrous decade meaning pay remains below pre-crisis levels,” he said. “But there have been notable exceptions. Britain’s lowest earners enjoyed the strongest pay rises last year as a result of another big increase in the national living wage.

“The strong pay performance for the lowest earners – on both an hourly and a weekly basis – fully vindicates that ambition of both main parties for a higher minimum wage. But more work will be needed to get everyone else’s pay packets beyond where they were before the crisis.”