Distrust toward the Social Insurance Agency and the Ministry of Health, Labor and Welfare only continues to grow.

Literal

Social-Insurance-Agency [and-や] MHLW [toward-への] distrust-feeling [topic-は] build-up [one-direction-一方である].

Editorial register. ~一方である ('to continue only X-ing, to keep building up in one direction') is a fixed expression for unrelenting change. 募る ('to grow stronger, to build up, to intensify') is used with feelings and negative emotions. ~への is the composite particle 'toward X + attributive.' 不信感 ('feeling of distrust') uses the ~感 suffix for 'sense of X.' Typical of an op-ed about government scandals.