Clive Baulch has fallen a long way in a short time. In April 2012 he was managing a team of social workers and taking home £2,000 a month. When he was made redundant, he thought finding another job would be easy. By October, he was desperate to find work, out of savings and reliant on £71 a week jobseeker's allowance. On 15 November, he went to sign on as usual. The Friday before, he had been on a day-long job trial, but otherwise it had been a quiet week. "My adviser took one look at my booklet and said she was sanctioning me, 'for not looking for work diligently enough'.

"Your money stops immediately," Baulch continues. "Thereafter, you are in freefall." He said he often waits until midnight to go through supermarket bins around his south London home. He has also at times gone begging – "not something I'm proud to say … but you have to think in survival terms". Missing so many meals caused complications with his diabetes, leading the doctor to sign him off sick – though his sickness benefit still hadn't come through when he was interviewed in February.

Iain Duncan Smith and other Department for Work and Pensions ministers deny that jobcentres have any targets for increasing the number of people whose jobseeker's allowance is taken away – but a host of evidence suggest otherwise. A total of 680,000 sanctions were handed out in the 10 months up to October 2012, already more than in the whole of 2011, according an analysis of figures from the DWP. When a jobseeker is sanctioned, it means their benefit is reduced to zero for weeks or months if it is deemed they are not trying hard enough to find work.

The increase has been fuelled by a shift in the culture in jobcentres. Staff are being put under pressure by managers to halt claimants' money even when they do not consider this to be appropriate or fair, according to interviews the Guardian has conducted with more than 10 jobcentre staff from around the country over the last 12 months.

"It's all about stopping people's money," said an adviser in Scotland, speaking on condition of anonymity, who was put on a "performance improvement plan" for failing to impose enough sanctions. "I got told … I need to get X amount of sanctions by March – about two a week," he said.

Jobcentre employees across the country say that as a direct result of this sort of pressure – they are now expected to hit a "minimum expected level" of sanctions – vulnerable claimants are often unfairly penalised. These include "people with language difficulties, people who can't read or write, or have learning disabilities" according to an adviser in Kent. He says his office has had "name and shame" boards featuring staff members' sanction records.

Other evidence seen by the Guardian includes a photograph from a jobcentre in Derbyshire showing sanctions marked by stars, and a bold title saying "as an office, we should be looking to make at least eight referrals … a day". Jobcentre employees make referrals to "decision makers" who rule on whether to apply the benefit sanction; about 70% of referrals are approved.

One set of minutes from a staff meeting in a Buckinghamshire jobcentre in January record a local manager as saying: "We are still falling short of the DMA [sanctioning] activity expected for [this area], therefore minimum expected actions are now set for each personal adviser … each PA is expected to take two stricter benefit regime actions [referrals] per week … performance improvement plans would have to be considered for non-compliance."

Despite these comments, the DWP said its policy is "very clear – we do not set targets or use league tables". Officials only "monitor sanctions to identify if any one jobcentre is performing wildly different to the norm. This is not a target, but helps us to check sanctions are being applied correctly. Only claimants who have genuinely failed to comply with their obligations are sanctioned. We are very clear about that."

There are also suggestions that employees are also penalised for not doing enough. They describe working in a system dominated by acronyms, targets and benchmarks: performance improvement plans (known as Pips) given to staff members who don't meet "minimum expected levels" (Mels); the junior manager pushed to Pip staff who don't meet their Mels or face a Pip himself; the decision maker whose "productivity" – the number of decisions they have to make in a day – has been gradually pushed up, meaning they no longer have enough time to make proper inquiries into a case before stopping a claimant's money.

Dave Green, 30 years in his job as an adviser in Scotland, prides himself on understanding his customers, and having one of the best records at finding them work. But he described being constantly harassed and told he is not doing his job properly for not meeting the expected level of sanctions. Green (not his real name) said he has been put on a Pip by his manager and told he needs to stop an average of two people's benefits a week.

The Trussell Trust, the largest food-bank provider across the country, said 44% of its referrals are now due to "benefit changes or delays. John Williams runs the Storehouse community centre and food bank on the Queensway estate in Southend. He said there was one word he had been hearing more and more from the people joining its growing list: sanctions.

On the Wednesday morning when the Guardian visited the food bank, the queue stretched around the block. People were filing into a storeroom lined floor to ceiling with donated tins, bread and nappies. Each was allowed to choose eight items, and the scene resembled a bustling market, with plenty of gallows humour. "Horsemeat chilli?" asked one punter, pointing to a tin on the shelf.

Meanwhile, Clive Baulch is also speaking out, risking, he said, "demonisation" in the press and "victimisation" at the jobcentre because he believed it was his right to be supported.

"I've been paying into the system for 30-odd years," he said. "But when I came to sign on, the attitude is 'you're scum … you have no rights'. I used to be a social worker, now I'm nothing."

The DWP said the reality is different. A spokesperson said: "A decision on whether someone is sanctioned is made independent of jobcentres and based on evidence. There is also a right to an independent appeal."