Councils have been accused of deliberately hiding the scale of the rough sleeping crisis in England by changing the way they compiled figures for the 2018 official count, the Guardian can reveal.

Official government statistics reported a 2% fall in rough sleeping in England in 2018 after seven consecutive years of rises when the figures were released last month. But critics have suggested the percentage decreased after several councils changed their counting method and does not reflect the reality on the streets.

The government has described the claims as “an insult” to the volunteers and charities who help compile the official figures. But back in 2015 the figures were also criticised as low-quality, untrustworthy and vulnerable to political manipulation by the UK Statistics Authority who threatened to remove their official status.

The rough sleeping statistics for England, based on a combination of estimates and spot counts on a single night in autumn, are intended to include everyone about to bed down or already bedded down on the street, in doorways, parks, tents and sheds but not hostels or shelters.

Estimates, akin to a local census, are typically agreed by agencies who work closely with rough sleepers in the area all year round, whereas street counts are one-night snapshots.

Analysis by the Guardian found that more than 30 councils switched from submitting an estimate to a street count from 2017 to 2018, with some councils reporting reductions in rough sleeping of up to 85%.

In Brighton and Hove, the official number for rough sleepers fell from 178 to 64 people in 12 months after the council made the change. Opposition councillors have described the drop as a “deliberate misrepresentation” of the scale of rough sleeping in the area.

Conservative councillor Robert Nemeth at Brighton council said: “Physically counting produces lower figures as it will always be the case that not every rough sleeper can be found on any given night. This happened in November 2018 when the count was conveniently carried out when it was snowing. It produced a figure that was under half of what the city’s rough-sleeping campaigners estimated as the real number.”

In Southend-on-Sea, there was officially an 85% reduction in rough sleeping from 2017 to 2018, according to the most recent figures, from 72 to 11 people, following a change in the counting method. Local charities have questioned the validity of the figure.

Authorities in Redbridge, Eastbourne, Medway, Worthing, Thanet, Exeter, Basildon, Ipswich, Warwick and Gloucester all reported big falls in rough sleeping from 2017 to 2018 after switching from reporting an estimate to a street count.

Homeless charities have long felt the official figures fail to capture the true scale of rough sleeping in England. Last December, Crisis estimated that more than 22,000 people in England would spend the festive period sleeping rough or in cars, trains, buses or tents, more than four times the official figure of 4,677 for 2018.

The accuracy of official rough sleeping statistics is important as central government uses the figures to allocate funding and make policy decisions about how to best tackle the homelessness crisis in England.

Concerns have previously been raised about the number of local authorities that reported having no rough sleepers in the official figures for England, which rose for the third consecutive year in 2018, including homelessness hotspots such as Gosport, Hampshire.

When contacted by the Guardian, several local authorities that changed from reporting an estimate to a street count said they had been advised to do so by the Ministry of Housing, Communities and Local Government after receiving money through the Rough Sleeper Initiative, a short-term fund aimed at reducing rough sleeping in the most affected areas.

Homeless Link, which is paid by the central government to guide councils on collating rough sleeping statistics and officially verify the count, said local authorities are free to choose to do a count or an estimate each year.

In response to the figures, minister for homelessness MP said: “These claims are an insult to the hardworking outreach workers, local charities, and other groups that collate these figures and are independently verified by Homeless Link.

“The rough sleeping count uses a well-established method – adopted by many cities across the world – providing us with a reliable way of comparing change over time, and councils have the freedom to choose how they conduct their count to best suit their area and individual circumstances.

“We have set out bold plans to end rough sleeping – and these figures show our work is already making a difference.”

‘Absolute rubbish’

It is a mild afternoon in Southend-on-Sea, Essex, and Mike, a 57-year-old rough sleeper, is watching the half-term chaos pass him by on the bustling high street. Just hours before, Theresa May congratulated the borough council on an apparent 85% reduction in rough sleeping in just 12 months. Officially, the number of rough sleepers in the area, which also includes nearby Westcliff-on-Sea and Shoeburyness, plummeted from 72 people in 2017 to just 11 in 2018. But nobody who works with Southend’s street population is convinced by the official figures, let alone the rough sleepers themselves.

“Absolute rubbish,” chuckles Mike, a former paramedic who suffers with a terminal respiratory illness. Like many coastal towns at the end of a train line, Southend and the surrounding communities have felt the brunt of England’s homelessness crisis. Shelters and churches are full throughout the winter, soups kitchens regularly feed around 40 people in Southend alone, and the high street is punctuated by sleeping bags and piles of cardboard.

Homeless people asleep on the streets of Southend-on-sea. Photograph: Penelope Barritt/Alamy Stock Photo/Alamy Stock Photo

In 2017, the borough had the ninth highest rough-sleeping population in England, according to government statistics. A year later, Southend is not even in the top 100. But that’s not the full story.

Every year since 2010, with the exception of 2014, Southend borough council submitted a figure based on an estimate, akin to a local census, of its rough sleeping population agreed by agencies that are in regular contact with the area’s homeless. Rough sleeping surged, from just eight in 2010 to 72 in 2017, notwithstanding a dip in 2014. But last year, the council changed its methodology and submitted a street count of rough sleepers seen on one especially cold night in late November. Councils are allowed to make the change under government rules and Homeless Link guidance but it has a big effect on what’s being officially recorded.