Sarah O’Connor moved to Britain from Jamaica 51 years ago, when she was six, and has lived here ever since. Last year she was challenged by the benefits agency to prove she was in the country legally, unleashing a torrent of immigration-related problems. For the past nine months she has been left facing bankruptcy, afraid to open the front door in case it is the Home Office coming to deport her or bailiffs arriving to remove her property.

O’Connor is unable to provide documentary evidence to prove she is here legally. Without this paperwork, she has been unable to take up new work and has been refused unemployment benefits, leaving her without an income. She sold her car at the beginning of the year, but she is struggling to pay her rent and is falling further into debt.

She is one of a growing group of long-term UK residents who arrived as children from Commonwealth countries in the 1960s and are now facing complex problems as a result of the introduction by the government in 2013 of a hardline immigration policy known as “hostile environment”.

O’Connor’s difficulties emerged last summer when she lost her job in a computer shop where she had worked for 16 years. When she applied successfully for a number of new jobs, she found she was unable to take them up because they asked her for a British passport, which she does not have. When she went to the jobcentre to apply for benefits to tide her over while she tried to sort the problem out, she was told she was not eligible.

Having lived in the UK for more than half a century, attending primary and secondary school here, working continuously, paying taxes and national insurance, holding a driving licence and voting in general elections; having been married for 17 years to someone British and having had four children here (all of whom have British passports), she is puzzled as to why her immigration status is being questioned.

“It was the way they treated me because I didn’t have a British passport. I said I’ve had no reason to go out of the country so I’ve never applied for one. They made me feel like I’m not British. I came home and cried,” O’Connor said. Debt companies have written to say they will be visiting to see which of her belongings they can take away to sell at auction.

“I can’t get another job without proving I’m legal and I can’t get the documents to do that. The stress of it is making me ill. When the doorbell goes I worry if it’s not the debt enforcers it’s going to be the immigration people, telling me I don’t belong here and trying to send me back to a country I don’t know.”

Her difficulties came to light after media coverage of Paulette Wilson, who was sent to an immigration detention centre despite having been in the country for 50 years, and Albert Thompson (who has asked for his real name not to be revealed), who is currently not receiving cancer treatment after being told he would need to pay £54,000 for it, despite having lived in London for the past 44 years. Numerous other cases have emerged of people who have lost their jobs or been made homeless because they are unable to provide documentary evidence of their right to be in the UK.

O’Connor never applied for a British passport. “The furthest I’ve ever been is the Lake District. I didn’t know that I needed to have a naturalisation number; I didn’t even know what that was,” she said.

She has tried to sort out her lack of paperwork, but has been unable to pursue the first stage because it requires a £237 initial payment and the whole naturalisation process costs over £1,200 – money she does not have since she is unable to work. After O’Connor’s case was raised by the Guardian with the Home Office, an official called her on Wednesday and promised to send forms so she could apply to remain. When she said she was unable to pay the fee, another official called her back to say the fee could be waived for her.

She is bewildered by an offer of help that has come only when her case looked set to attract media attention, and she remains uncertain about whether she will be able to find enough documents to prove she has been here a lifetime. Initial attempts have proved unsuccessful. Her MP’s office contacted the Home Office on her behalf and was told: “I have searched our systems and can find no Home Office record for Ms O’Connor.”

O’Connor has contacted the National Archives to see if they can find a record of her immigration status and was told: “Unfortunately I could find no entry for your name.”

Sally Daghlian, the chief executive of Praxis Community Projects, which has supported more than 120 people in situations similar to O’Connor’s, said: “The burden of proof is astonishingly high. An individual has to produce a minimum of one but preferably four pieces of documentary evidence for every year they have been in the UK. Documents dating back decades must be sought from the tax office, DWP and other official sources. In many cases such records no longer exist.”

She said the introduction of the hostile environment was increasing the prevalence of racist decisions. “Non-immigration specialists (doctors, administrators, civil servants, landlords) are now required to check immigration status before delivering services. This inevitably leads to discriminatory requests for passports, as judgments are being made on the basis of colour, accent, ethnicity and can result in racist practices.”

In the 1970s and 80s O’Connor worked in a greengrocers and for Ford Dagenham as a cleaner, but she doesn’t have paperwork to prove it. “Wages weren’t paid straight into bank accounts then. I don’t have the payslips; I keep receipts and paper slips for six years – then I throw them away. If I didn’t the house would overflow with paperwork,” she said. “It’s so ridiculous. I see myself as British. The government was happy taking my taxes and national insurance payments for 30 years.”

A Home Office spokesperson said: “We understand these individuals may not have the relevant documentation to support their application, and so we work closely with applicants to consider alternative documentation to prove their ongoing residence. Those who have resided in the UK for an extended period but feel they may not have the correct documentation confirming their leave to remain should take legal advice.”

O’Connor said she was puzzled by the suggestion that she seek legal advice. “People in my situation can’t pay the fees because we’re not allowed to work. How can I get legal advice without money?”