Under the previous boundary, Oakwood Riding School was outside the growth area.

However, under legislation introduced to State Parliament last week, the boundary has been further expanded, meaning the riding school could be saddled with a Growth Areas Infrastructure Charge bill of $3.8million.

If the bill becomes law, the $95,000-a-hectare GAIC will apply to affected properties sold in Officer, Clyde and Devon Meadows.

Oakwood director Michael Hocking, a member of GAIC protest group TaxedOut, said the riding school felt duped because it didn't make a submission to the Government's latest plan.

"We hadn't contacted the Government on the basis that we had been taken out of the boundary [in the previous version]."

The Liberal-National Coalition and the Greens have indicated they will block the legislation in the Upper House.

Planning Minister Justin Madden said the Opposition's actions were scandalous and irresponsible.

"If they pursue this course they will be directly responsible for forcing land prices up, increasing the cost of housing by up to $30,000, freezing Victorian families out of the housing market and denying these communities vital schools, health care, roads and public transport."

Bass Liberal Ken Smith said the charge should apply at the point of development, which could be 10-15 years later.

He said landowners wanting to sell up in the meantime would not receive the "windfall gains" promised by the Government.