Hundreds of cancer patients are being placed on the Job Seeker Hardship, making it harder to gain financial support for their treatment, in what the Cancer Society says is "ludicrous".
The move came after the sickness benefit was replaced by the Job Seeker Hardship in 2013.
A cancer patient who did not want to be identified told Radio New Zealand she had to pay for a medical certificate every month to prove she was not fit to work. Her surgeon told her she wouldn't be able to work for much longer.
"The letter from the hospital wasn't sufficient. I then had to go back and get a doctor's note to keep them happy, just to prove the fact that I was going in for surgery," she told the national broadcaster.
"Then I also had to, on the day of my surgery, get someone from the hospital to fax through that I had been operated on," she said.
Cancer Society chief executive Claire Austin said the woman's story was common, and the system lacked common sense and sensitivity.
Many cancer patients had never been on a benefit before and needed support when going through their treatment, she told Radio New Zealand.
"The situation really is ludicrous. We've got people who are already in work, who are unable to work because they are either sick and have to go through treatment, or have surgery.
"They have to then apply for a benefit, which is a benefit that requires them... to be available to work," she said.
Although cancer patients did not have to attend job seminars and interviews, it was still difficult to get and maintain financial assistance.
"People have to go through appointments, they have to go through the various forms. Then they have to get the medical information as well. I mean really, it should be made very simple. It could be made so much simpler."
Minister of Social Development Anne Tolley told Radio New Zealand she requested the MSD to discuss with the Cancer Society to streamline the process.
"We are always willing to have a look and see if there is something we can do to help," she said.
However, Ms Tolley said: "We're not going to start pulling apart what was redesigned as a pretty simple system, not for us but for people accessing it."