As reported in the Evening Times earlier this week, Neil Couling, Work Services director of the Department and Work and Pensions, told the Scottish Parliament Welfare Reform Committee more people were using food banks because free food was available and said poor people were "maximising their economic opportunities."
In response to claims welfare reforms were driving greater need for food banks, he said that was wrong and groups like the Trussell Trust were "looking at what people are reporting at food banks".
Mr Couling also said the trust set up food banks as an "evangelical device" to get in touch with people in communities.
Ewan Gurr, Scotland Development Officer with the Trussell Trust, said evidence given was consistent with the Trust view that the growth in food banks was in response to growing demand and welfare reforms were the main driver of that demand.
He said: "Neil Couling, Work Services Director for the Department of Work and Pensions, confronted the credibility of these two key points in his presentation to you and made some comments about our work that are unsubstantiated and extremely disappointing."
The chairman of the Trussell Trust, Chris Mould, has written to Mr Couling asking him to withdraw his remarks.
He said: "When the Trussell Trust reports data from its data collection system, it is not primarily "looking at what people are reporting in food banks".
"We are aggregating what more than 24,000 voucher holders have told our food banks about the reasons they are referring their clients to us. They sign these forms to validate their requests and all referrals are traceable and auditable. Around half the voucher holders are public servants. We are sorry that you seem to be belittling the work of the Trussell Trust food banks and calling into question the credibility of the volunteers and project managers running them."
On the evangelical claim, Mr Mould added: "Please provide me immediately with the evidence you have to support this assertion.
"You are directly challenging the integrity of a registered charity and its trustees both past and present.
"If you are not able to provide evidence to support this assertion please write immediately to the Scottish Parliament Welfare Reform Committee to withdraw the statement."