A powerful House Republican wants the Obama administration to explain why it’s asking for an extra $111 billion to implement part of the healthcare reform law.

Ways and Means Committee Chairman Dave Camp (R-Mich.) is asking about a spike in the estimated costs of subsidies to help people buy private insurance — a central, and expensive, component of the new healthcare law.

The administration’s budget request this year included $111 billion more for subsidies than its request last year. The difference falls across the same seven-year window.