Melanie Woolcock was not well enough to work and receiving benefits when she was sentenced

In July 2016, Melanie Woolcock, a single mother from Bridgend in Wales, was given an 81-day jail sentence for failing to pay her council tax. Not well enough to work and receiving benefits, she had racked up £4,742 in council tax debts.

A court initially ordered her to pay £10 a week towards her arrears. While she kept up the payments for a few months, Woolcock eventually defaulted and was sentenced in her absence. Despite making a last-minute payment of £100, on 8 August, bailiffs and two police officers went to her home and took her to Bridgend police station and then to HMP Eastwood Park.

“I was being treated exactly the same as someone who had murdered somebody,” she said after her release. “But when you’re in there and you feel you haven’t committed a crime, you feel a vast injustice being done to yourself.”

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She is one of 305 people sent to prison in the past six years in England and Wales for failing to pay their council tax, according to government figures released following a freedom of information request by the Guardian. There were 6,278 suspended sentences handed out for the same offence in that period.

Regulation 47 of the Local Government Finance Act 1992 states people can be given prison sentences for not paying council tax only if they have done so due to “wilful neglect or wilful refusal”, meaning those who have fallen into arrears because they can’t afford to pay should not be imprisoned. But campaigners say many of those given jail terms have acquired the debts because they can’t afford their bills.

Woolcock was released from prison after 40 days following an appeal. A judge found magistrates had failed to conduct a proper inquiry into her means before sentencing. A subsequent high court judgment ruled magistrates were making mistakes and wrongfully imprisoning people in 9.5%-18% of cases, but while “that level of error by magistrates is of concern and unacceptable”, it was too low to suggest “a problem inherent within the system”.

Following Woolcock’s case, the Welsh government decided to abolish custodial sentences for non-payment of council tax – a change that comes into force this month. Scotland and Northern Ireland do not punish non-payment of local taxes with prison.

In another case, a woman in her 40s from Kent, who asked to remain anonymous, was committed to a closed women’s prison for 90 days for a council tax debt of £2,684.28.

“They kept moving me from cell to cell, from one house block to another,” she said. “I was scared every night in case I got stabbed.” She said she was still suffering the effects. “I’m still suffering to this day … It makes you always look over your shoulder,” the woman added.

Samuel Genen, a solicitor who represented both Woolcock and the woman in Kent, said he did not trust the figures from the Ministry of Justice in response to the Guardian’s FoI, as information provided in the past had often been incomplete and wrong.

“The problem with imprisonment for council tax in England is simply the system gets it wrong,” he said. “Poor people are wrongly imprisoned and the government chooses to do nothing.

“The government had a choice, and even after being told that more than 15% of people a year are sent to jail unlawfully, they have chosen to do nothing … I regrettably have no answer as to why no one in government has acted.”

Naima Sakande, a women’s justice advocate at the Centre for Criminal Appeals, which has been campaigning for a law change, said the poorest were being hounded by some councils, which used the threat of imprisonment to obtain the money from them.

“Prison should be reserved for the most serious of offences. It is unconscionable that we use the sanction for such a thing as civil debt,” she said. “Poverty is not a crime. England must step into the modern world and abolish imprisonment for council tax debt.”

Alistair Chisholm from the debt charity PayPlan, who has conducted research into the use of imprisonment for council tax debt, said there had been a lot of focus on how the private sector collects debts, but less on the public sector.

“On the back of PPI scandals and aggressive debt collection after the financial crisis, the George Osborne government introduced more regulation on debt collection, but they didn’t apply it to themselves,” he said.

A Bridgend county borough council spokesperson said of Woolcock’s case: “Local authorities have a responsibility to recover unpaid council tax, but have no influence over court decisions.

“We understand that in this specific case the resident was jailed after failing to meet the requirements of the suspended sentence which had been issued by the magistrates court. Our advice to anyone who is experiencing difficulty in paying their council tax is to contact us as early as possible so that we can help and advise them.”

• This article was amended on 15 April 2019. An earlier version incorrectly referred to PayPlan as a debt charity whereas it is a free debt advice provider.