I read your article on Iain Duncan Smith's proposal for a "welfare revolution" with a sense of despair (Duncan Smith starts welfare revolution, 27 May). The work and pensions secretary enlists a familiar set of cliches in his attempt to portray the British welfare system as "bust", while simultaneously displaying a worrying ignorance about how the system actually operates.

I worked in one of Jobcentre Plus's contact centres for over two years, taking benefit claims over the phone in scripted telephone interviews. I took claims for employment and support allowance (ESA) from the day it was launched. Duncan Smith cites incapacity benefit (IB) as an example of how the welfare system fails society: "People basically get parked on this benefit and forgotten about." ESA was introduced in October 2008 specifically to address this. The extension of the harsher work capability assessment to existing IB claimants is a long-standing Labour project, and for him to take credit for it, even by implication, is unfair.

In a BBC interview he described ESA as a "disability benefit" for those with the potential to work. This is highly inaccurate. It is a benefit intended for those suffering short-term illnesses as well as long-term disabilities, and is intended as a replacement for IB, not to supplement it. It is disturbing that the man in charge of the welfare system does not seem to properly understand one of its key benefits.

In effect, ESA is designed to deal with the large numbers claiming for moderate depression, back pain and similar conditions. Of those who are genuine, most would be better off in work. These represented about 60% of sickness claims I took. Dealing with this problem is necessary, but the blunt instrument of ESA has created countless innocent victims. A colleague's bipolar brother recently became suicidal on receiving the letter calling him for his capability assessment.

Duncan Smith repeats another cliche – that people are better off on benefits than working. He states: "If you are unemployed, and you come from a family that is unemployed, all you can see when you think about work is risk." In fact, very few are materially better off unemployed, as there are numerous financial incentives to ensure that taking a job is financially rewarding. Jobcentre advisers are trained to offer "better-off calculations" that detail claimants' potential earnings from these benefits.

A major factor behind long-term unemployment is that the slender rewards of taking poorly paid work aren't compensated for by the additional stress involved in taking some of the worst jobs in society. Given a choice between receiving £60 a week to do nothing and £80 a week to clean toilets, most of us would opt for inactivity. No restructuring of the system is going to compensate for lack of opportunity.

With this in mind, Duncan Smith's promise to re-incentivise work has sinister implications. The easiest and cheapest way to do this is to slash benefits to a level where they can't sustain a tolerable lifestyle. This is what I suspect is planned, despite all his talk of reform.