Image copyright PA Image caption Wormwood Scrubs, Hull, Lindholme and Nottingham were among the 10 prisons given extra funding

Levels of violence and drug taking have fallen since last year at some of England's "most challenging" prisons, the Ministry of Justice (MoJ) has said.

The rate of assaults fell by 16%, while failed drug tests also dropped across the 10 prisons that were given £10m extra security funding in 2018.

But in three of the jails, Hull, Nottingham and Wormwood Scrubs, the rate of assaults increased.

Ex-minister Rory Stewart had vowed to resign if the prisons did not improve.

However, he was promoted to secretary of state for international development in May and then resigned in July anyway over Boris Johnson's Brexit plans, before the impact of the project on drugs and violence levels was known.

The percentage of failed drug tests across the 10 prisons halved between August 2018 and March this year, the MoJ said, although its report pointed out that the number of prisoners sampled was small.

As part of the scheme - given the name the "10 Prisons Project" by the MoJ - governors were given extra funds to spend on measures including for new X-ray body scanners, sniffer dogs, extra staff and basic repairs.

The MoJ said the project, which ran for a year from June 2018, had now finished but added that it would form "part of our continuing efforts to boost safety, security and decency in all prisons".

How assault rates changed During the 10 Prison Project Prison % Start (June - August 2018) % End (April - June 2019) Hull 28.6 29.1 Humber 47 28.1 Isis 66.7 36 Leeds 46.9 43.4 Lindholme 55.1 29.7 Moorland 37.4 24.6 Nottingham 50.2 60.4 Ranby 41.4 32.4 Wealstun 36.5 30.2 Wormwood Scrubs 29.5 48.5 10 Prisons Total 42.9 36.1

The figures showed that the rate of assaults per 1,000 prisoners across the 10 jails fell from 42.9 in the three months to August last year to 36.1 in the quarter to June - a decrease of around 16%, compared with a drop of roughly 8% across all prisons in England and Wales.

Lucy Frazer - who replaced Mr Stewart as prisons minister - said she was "encouraged" by the new figures.

"We are already using what has worked to improve the rest of the estate, spending £100m on airport-style security to stop the scourge of mobile phones and drugs that fuel crime and disorder in jails," she added.

But critics of the scheme said the MoJ's project did not go far enough.

Image copyright UK Parliament' Image caption Prisons minister Lucy Frazer said the project will influence future spending by the MoJ

The chief executive of the Howard League for Penal Reform, Frances Cook, said the measures "will fail to deliver if prisoners are given nothing to do and released with nowhere to live".

She added: "Tightening security in a few troubled prisons is all well and good, but ministers will have to take a different approach if they want to tackle the problems in more than 100 jails across the country."

How drug taking fell During the 10 Prison Project Prison % June - August 2018 % Apr - June 2019 Hull 14.6 10.2 Humber 26 10.6 Isis 22.6 12.5 Leeds 11.5 13.2 Lindholme 39.1 6.1 Moorland 27.1 12.5 Nottingham 16.7 22.5 Ranby 33.3 14 Wealstun 31.7 6.8 Wormwood Scrubs 33.3 21.3 10 Prisons Total 26.5 13.3

The charity Prison Reform Trust welcomed the reduction in violence but warned that the 10 prisons project and the fate of a prisons minister "always risked being a distraction from the real issue" of overcrowding.

A spokesman added: "Any glimmers of systemic improvement will be quickly snuffed out if we return to the failed 'prison works' policies that have created this calamity in the first place."

The government has also pledged to recruit thousands of extra prison officers and create 10,000 additional prison places in England and Wales.