The homelessness minister, Heather Wheeler, has apologised after leaked emails showed her using “racist” language to describe rough sleepers before she joined the government.

In an email sent in October 2017 to a homeless charity three months before she became minister, the Conservative MP for South Derbyshire described rough sleepers in her constituency as “the traditional type, old tinkers, knife-cutters wandering through”.

The email emerged during filming of a Ross Kemp ITV documentary that will air next month investigating discrepancies in the official rough sleeping figures in England, which are used to determine vital funding to tackle homelessness and which the UK statistics regulator has warned should not be trusted.

Wheeler’s comments prompted Stephen Robertson, the chief executive of the Big Issue Foundation, to call on her to resign. He said: “The use of pejorative terminology to describe marginalised people has no place in this day and age; it serves only to stigmatise individuals, questioning their fundamental legitimacy and reinforcing the impossibility of tackling societal challenges.

“This is not a matter of undue political correctness, it reflects the need we have to embrace diversity and equality in modern Britain, stamping out obsolete attitudes once and for all. In light of her comments it is only appropriate for Heather Wheeler to resign.”

Wheeler issued an apology for her “inappropriate language”, and said it “is not at all representative of the great cultural contribution and rich heritage that the Gypsy, Roma and Traveller communities make to this country”.

Michelle Gavin, from Friends, Families and Travellers, a leading national charity working on behalf of Gypsies, Travellers and Roma, said the language was “disgraceful”.

“The word ‘tinker’ is a racist term used to put down Irish Travellers. To think that a government minister is using this language is disgraceful,” she said.

“Irish Traveller children should not have to grow up in a society where government ministers show such contempt for their culture, heritage and identity.”

The Labour MP Alex Cunningham, the shadow housing minister, asked how anyone could have confidence in a minister who “dismisses homeless people with such shocking and shallow views”. He added: “Government ministers must understand the problems of homelessness in order to fix them, and they’re failing.”

Quick Guide Rough sleeping and homelessness in the UK Show Is rough sleeping getting worse? The government claims rough sleeping in England fell for the first time in eight years in 2018, from 4,751 in 2017 to 4,677. But the body that oversees the quality of official statistics in the UK has said the number should not be trusted after 10% of councils changed their counting methods. Rough sleeping in London has hit a record high, with an 18% rise in 2018-19. The numbers of people sleeping rough across Scotland have also risen, with 2,682 people reported as having slept rough on at least one occasion. Shelter, whose figures include rough sleepers and people in temporary accommodation, estimate that overall around 320,000 people are homeless in Britain. What’s being done about rough sleeping? The government’s Homelessness Reduction Act 2017, which places new duties on state institutions to intervene earlier to prevent homelessness has been in force for more than a year, but two thirds of councils have warned they cannot afford to comply with it. In 2018, James Brokenshire, the housing secretary, announced a one-off £30m funding pot for immediate support for councils to tackle rough sleeping. How does the law treat rough sleepers? Rough sleeping and begging are illegal in ENgland and Wales under the Vagrancy Act 1824, which makes ‘wandering abroad and lodging in any barn or outhouse, or in any deserted or unoccupied building, or in the open air, or under a tent, or in any cart or wagon, and not giving a good account of himself or herself’ liable to a £1,000 fine. Leading homelessness charities, police and politicians have called on the government to scrap the law. Since 2014, councils have increasingly used public space protection orders to issue £100 fines. The number of homeless camps forcibly removed by councils across the UK has more than trebled in five years, figures show, prompting campaigners to warn that the rough sleeping crisis is out of control and has become an entrenched part of life in the country. Is austerity a factor in homelessness? A Labour party analysis has claimed that local government funding cuts are disproportionately hitting areas that have the highest numbers of deaths among homeless people. Nine of the 10 councils with the highest numbers of homeless deaths in England and Wales between 2013 and 2017 have had cuts of more than three times the national average of £254 for every household. What are the health impacts of rough sleeping? A study of more than 900 homeless patients at a specialist healthcare centre in the West Midlands found that they were 60 times more likely to visit A&E in a year than the general population in England. Homeless people were more likely to have a range of medical conditions than the general population. While only 0.9% of the general population are on the register for severe mental health problems, the proportion was more than seven times higher for homeless people, at 6.5%.

Just over 13% of homeless men have a substance dependence, compared with 4.3% of men in the general population. For women the figures were 16.5% and 1.9% respectively. In addition, more than a fifth of homeless people have an alcohol dependence, compared with 1.4% of the general population. Hepatitis C was also more prevalent among homeless people.

Sarah Marsh, Rajeev Syal and Patrick Greenfield

Wheeler, who promised when she took the job to step down if she failed to halve rough sleeping in five years, has heralded an apparent 2% fall in rough sleeping in England in 2018 despite accusations that some councils have deliberately under-reported the figures.

South Derbyshire, where Wheeler is an MP, reported having no rough sleepers in 2018. But the film crew for Ross Kemp: Living with Homelessness interviewed a man who called himself Ebenezer Goode and said he had been sleeping rough in the constituency for 32 years and was surprised not to be included in the estimate submitted for the national count.

A charity in nearby Burton said it had frequently provided services to rough sleepers from Wheeler’s constituency in the last few years. In response to an offer of help from John Anderson of Burton Hope in October 2017 to support people on the streets in her constituency, Wheeler wrote: “Historically rough sleeping in South Derbyshire has been the traditional type, old tinkers, knife-cutters wandering through.”

Goode was known to Wheeler, his MP. In the same email to Anderson she said she was aware of his presence in the area. “More recently the district council looked after a man who slept by the offices, rehoused him a few times but he kept going back on the street and is still seen around Swadlincote,” she wrote.

She later confirmed she was referring to Goode. “[He] has been known to council officials for some time. [I] spoke to Goode, explained to him that the Homelessness Reduction Act introduced new duties on councils to support those who are, or at risk of becoming homeless.”

Despite this, Wheeler congratulated South Derbyshire on recording a rough sleeper estimate of zero. “I am delighted,” she told Derbyshire Live, a local paper.

When asked why she congratulated the council for having no rough sleepers, she said that a return of zero “does not imply there are no rough sleepers in South Derbyshire throughout the year”.

Makers of the programme also contacted other areas where the count was zero, including Northumberland. The Rev Davey Falcus, from Ashington Life Centre, called this a “joke” and said there were hundreds of rough sleepers in Northumberland county council’s jurisdiction. The council said accurately counting or estimating the number of people sleeping rough within its jurisdiction was inherently difficult, “given the hidden nature of rough sleeping”.