THe risk of homelessness from the "bedroom tax" has been much discussed, but warnings are growing that the effects of another aspect of welfare reform could be far worse.

Agencies working with homeless people say there is increasing alarm in the sector about the impact of penalties imposed on benefit claimants.

Benefit "sanctions" are incurred by those claiming the out-of-work benefit employment and support allowance (ESA).

A much tougher approach from job centres, demanded by ministers at Westminster, has seen sanctions increased dramatically. Not only has the number of penalties imposed almost doubled since 2010, they can now be applied for longer periods. The Government's policy is designed to ensure those claiming out-of-work benefits are genuinely seeking work and can show they are active in doing so.

While the Government insists job centres have not been given targets to increase use of sanctions, agencies working on the ground with claimants say that is misleading.

While accepting penalties may be necessary for those who do not adhere to job-seeking plans, they argue that job seekers are frequently being sanctioned for minor transgressions, or on unfair or spurious grounds. The extent of this suggests staff are at least under pressure to maintain high levels of punishment, it is claimed.

An academic backed this theory last week, publishing an in-depth analysis of the impact of sanctions on housing. Dr David Webster, an honorary senior research fellow at Glasgow University's Urban Studies department, told a conference held by Homeless Action Scotland (HAS) there was "abundant evidence" of pressure on Department for Work and Pensions (DWP) staff to maximise sanctions.

He argues that the recession has seen fewer people leaving work voluntarily and a swift fall in the proportion of penalties which are imposed on the grounds that people have put themselves out of work. The biggest proportion of penalties now come from failing to attend interviews, failing to attend training or work placements or failing to actively seek work.

At the same time, UK wide, there were 860,000 sanctions in the year to October 2012, compared with around 500,000 in the last year before the Coalition Government took power.

"Ministers have not set targets, but they clearly have driven up sanctions through management action," Dr Webster says. "There is a huge volume of anecdotal evidence indicating that many sanctions are unfair, negligent or downright fraudulent."

He cites examples, such as job seekers having benefits cut for not responding to a letter which was sent to the wrong address, attending a hospital appointment, failing to meet arbitrary targets or being a few minutes late to sign on.

One of the issues may be that of departmental silos, Dr Webster claims. Housing does not come under the DWP, so it doesn't affect them. But he believes the system is deliberately leaving people with no income. He said: "Homeless people are particularly vulnerable. "

Penalties can be disputed and 53% of those who contest them are successful, he says. But fewer than one in five claimants do so. Further appeals to a tribunal are taken up by just 1.8%, but of those, 17% get the decision overturned. "The massive increase in success rates at tribunals suggests many of the extra sanctions are dishonest," Dr Webster says. "But few go to tribunal."

Hardship payments are available to those who are sanctioned. But this too is difficult for those in crisis, he adds. "Nearly all the homeless people affected will qualify. But often they can't manage the bureaucracy."

Dr Webster is calling for the new Scottish Welfare fund to be reformed to allow it to assist those affected by benefit sanctions. Meanwhile housing benefit and council tax benefit should be automatically protected when there is a sanction.

Robert Aldridge, chief executive of HAS, confirmed growing concerns about sanctions: "This is a ticking timebomb for homelessness, potentially a far bigger problem than the bedroom tax."

While homelessness and housing agencies can plan for the bedroom tax and help those likely to be affected, the apparently arbitrary nature of job centre decision-making prevents this in regard to sanctions, he explains.

"It is unpredictable who is going to have a sanction imposed, how long for and when it is going to happen," he said. "Often the decision is taken by a junior member of staff and we are not sure how consistently. Individuals are faced with virtually no money and the idea that they then have scope to keep money aside for the rent is unrealistic."

Mr Aldridge says forcing people into destitution and rent arrears helps no-one. "Look at the amount of time spent by people who are sanctioned trying to find money, rather than looking for a job; the time spent by job centre staff imposing and administering sanctions rather than helping people find work, and looking at the added pressure on homelessness agencies, this seems an acutely futile and counterproductive activity."

A spokesman for the DWP said: "It's only right that people should do everything they can to find work in return for benefits. We make it clear to people at the start of their claim what the rules are and that they risk losing benefits if they don't play by them.

"Sanctions are only used as a last resort and people who are in genuine need can apply for hardship payments. If someone disagrees with a decision, they can appeal. Our staff do not have targets for benefit sanctions."