A Montgomery County bill intended to spur economic development in the county would likely cut revenues by $13.4 million — nearly 80 percent of development taxes’ expected earnings — in the current fiscal year, county Office of Management and Budget Director Jennifer Hughes said in a memo to the County Council.

Revenues for fiscal 2013 — which starts July 1 — would be cut by $3.8 million, Hughes said, putting the total reduction at $17.2 million over the two years.