Jessica was 22 weeks pregnant and walked more than two miles to get to the food bank because she was too poor to take public transport. She was receiving Employment and Support Allowance for mental health problems after giving birth to a stillborn baby eight months before. After she failed to attend a "work focused" meeting one day, she was sanctioned.

Speaking to the Work and Pensions committee last month, welfare reform researcher Kayleigh Garthwaite described how the woman’s mental health problems spiralled, her debts mounted and she was forced to live off he sister's children's leftovers. Following her sanction, Jessica said: “I haven't had my fridge or cooker switched on for three weeks, I can’t afford the electric. I sold the telly last week – there was no point in keeping it ‘cos I couldn’t afford to use it anyway.”

This was just one rather damaging message about David Cameron’s benefit system, one of many that have been vocalised by charities, local authorities and politicians.

Yet when the prime minister announced on Saturday he was thinking of docking sickness payments for those who do not accept treatment for obesity, drug and alcohol problems, he was displaying a side to a future benefit reduction programme that he hoped would gain more sympathy.

The fat and the feckless would not be allowed to scrounge off hard-working citizens under a future Conservative government, he proclaimed. Although elements of his own party criticised the announcement, Cameron would have hoped it stuck with voters who say they are sick of paying for people who say they are sick.

But the contrast between this weekend’s announcement and the Jessica’s story shows what a fine line the government and the Conservatives are treading to prevent ‘fairness’ being seen as ‘nastiness’.

One change in particular threatens to scupper Cameron’s claim to be on the side of Britain’s hard working people. In an alteration to legislation that went largely unnoticed at the end of last month, the government introduced a pilot for 15,000 low-paid working universal credit claimants. Those participating in the mandatory scheme may find that their benefits are reduced if they do not actively seek to work more hours or increase their salary.

The change is important because this policy goes beyond targeting jobseekers, the sick and disabled. If penalises those who are hard at work, maintaining part-time, low-salaried jobs

Labour peer Baroness Sherlock said in the House of Lords before the secondary legislation was introduced: ‘If you have been on benefits and you get a job, you do not expect the department to ring you up at work saying, “Come and talk to me because you’re not working enough”.

‘I think that people who feel that they have escaped the tender ministrations of the jobcentre are going to be a little taken aback when they find that it starts following them to work.’

Sanctions can apply of claimants working less than 35 hours a week on minimum wage (typically £12,000 a year) who do not comply with the scheme. Failure may include failing to attend ‘job focused interviews’ or failing to apply for a job that might bring in extra hours. Welfare reform minister Lord David Freud says "tougher" conversations will be had with claimants after two months.

For claimants, one of the most worrying aspects of the programme – called work related requirements – is that it can apply to housing benefit (technically the housing cost element of universal credit). That’s potentially a chunk of your rent lost to the DWP if you do not take active steps to get a better-paid job.

The pilot starts in April and if successful, the government intends to roll the scheme out for most universal credit claimants. Data comparison from the DWP's Stat Xplore shows that 1,078,413 people in Britain are claiming housing benefit and in work – meaning they are likely to be on low salaries. That’s more than 1m working people who could potentially be affected by the policy if the reform is rolled out with universal credit.

This policy is ill-conceived because the Prime Minister is currently trying to prove that he is on the side of those who are slogging away every day in a job. It won’t work if the "hardworking people" he so often praises suddenly start finding they themselves could be Jessica.