PCS is pressing work and pensions secretary Iain Duncan Smith for a meeting to discuss sanctions targets.
Ministers and senior Department for Work and Pensions officials continue to deny such targets exist.
But recent stories in the media show targets are being set and performance management procedures are being used to put pressure on staff to increase the number of sanctions applied.
The letter requests a meeting to discuss “targets and target-like expectations” in light of the evidence.
It adds that the union is “increasingly concerned that [senior managers] have failed to acknowledge that these examples show that the practice is widespread and have not acted to change the conditionality/sanctions target culture in jobcentres”.
The union says it is unfortunate that employment minister Mark Hoban had previously turned down a request to meet to discuss the new sanctions regime.
Commenting on the evidence of targets, PCS general secretary Mark Serwotka said: “It is a gross injustice that, with our economy stalling as a direct result of this government’s mismanagement, ministers are turning the screw on people who are entitled to benefits.
“Jobcentre staff did not join the employment service to be in conflict with claimants, they joined to help people, and jobcentres should not be used by ministers to pursue their political prejudices.”
