Ministers are accused today of breaking a promise to introduce a reform to cut the huge number of benefit sanctions, plunging people into the misery of hunger and eviction from their homes in some cases.

A “yellow card” system, giving claimants 14 days to challenge a decision to dock their benefits on the grounds it was imposed wrongly, was pledged more than two years ago in October 2015.

But the Department for Work and Pensions (DWP) has now admitted that the move has been postponed because “an evaluation has proved complex” – and that no date for its implementation has been agreed.

The stance has been condemned by Frank Field, the chairman of the Commons Work and Pensions Committee, who highlighted the appalling distress that sanctions are still causing.

It comes as the number of sanctions starts to rise again, driven by an explosion in the number of punishments imposed on claimants of universal credit.

One constituent of Mr Field, the MP for Birkenhead, was recently docked benefits for missing an appointment to receive universal credit because he was in an operating theatre at the time.

The DWP later accepted it as a valid reason and issued a back payment. But, Mr Field said, “the damage had already been done. The loss of money resulted in my constituent being evicted.”

In another similarly alarming case, a man in the Merseyside constituency was sanctioned for missing a job centre appointment while he was in A&E.

On that occasion, he pleaded with hospital staff to ring the job centre – fearing his benefits would be lost – but the sanctioning went ahead.

“My constituent said ‘Please don’t tell my family first, tell Jobcentre Plus,’ even as he had to be taken to A&E, because he was so terrified of being sanctioned,” Mr Field told The Independent.

“People are being reduced to going to food banks because they are being left so hungry, or they are losing their homes, which the yellow card would prevent.”

The warning system was first promised in October 2015 by Iain Duncan Smith, then Work and Pensions Secretary, who was under growing pressure from MPs.

He told MPs: “People are notified of a sanction and it is imposed immediately afterwards. In some cases, claimants go on to challenge the decision and the sanction may be overturned.

“We will trial arrangements whereby claimants are given a warning of our intention to sanction and a 14-day period to provide evidence of good reason before the decision to sanction is made.”

The trial, in parts of Scotland, led to almost 500 people successfully explaining why they did not deserve punishment after being accused of failing to meet their commitments in return for benefits.

A year ago, the DWP said claimants from the trial were being interviewed to compile a “final report” for publication in Spring 2017, but it never appeared.

Instead, Mr Field has now been told, in a written parliamentary answer, that “the finalisation of the evaluation has proved complex” and there is no date for publication.

Meanwhile, the number of benefit sanctions is starting to rise again, after falling in 2016, driven by the controversial extension of universal credit.

The shake-up replaces six existing benefits with a single payment, but the six-week wait for a first award, since cut to five, triggered widespread condemnation.

In the year to October 2016, 133,301 sanctions were imposed on universal credit claimants – a figure that soared to 238,985 in the following 12 months.

“The tide of sanctions is already high but – far from that tide going out – it is now going into reverse and the numbers are going up again,” Mr Field added.

The Independent revealed how the Government was refusing to investigate evidence of a 30 per cent leap in the number of claimants going to food banks in areas where universal credit was introduced.

A DWP spokesperson declined to expand on when the warning system might be taken forward, saying only: “Findings will be shared once the final draft is agreed.”

The department acknowledged that the use of sanctions had risen, but said the increase in the year to October 2017 – after the expansion of universal credit – was only from 3 per cent to 4.8 per cent.

“These are figures which relate to some time ago, and in fact the rate of universal credit claimants with a sanction deduction has decreased since a peak in March 2017 and now remains fairly stable,” the spokesman said.

“This peak in early 2017 was the consequence of the department processing a backlog of outstanding decisions at the end of 2016.

“Sanctions are only used in a small minority of cases when someone has failed to meet the requirements without good reason.”

The benefit sanctions system has long fiercely criticised for causing hardship and depression, often on flimsy evidence of wrongdoing – and with little proof that they work.

Typically, if conditions are not met, benefits are docked for four weeks, which can mean a loss of £300 for a claimant over the age of 25 – but a sanction can last for three months, or even a year.

In a damning report in 2016, the National Audit Office castigated the DWP for failing to monitor people whose benefits had been docked and suggested the system cost more money than it saved.

In the six-month Scottish trial, around 6,500 claimants were given a yellow card, of whom 13 per cent provided evidence to challenge their potential sanction.

Of that 13 per cent, 455 then avoided being sanctioned – which means around half of the claimants who provided evidence made a successful challenge.