The New South Wales government has given the green light to a massive housing development on Sydney’s fringe despite the state’s environment minister expressing reservations last month about current koala habitat protections in the region.

The government has given approval to the project but the actual rezoning has been deferred until 15 December to give the government time to negotiate a state planning agreement with Walker Corp and allow the developer to finalise an infrastructure plan for the huge area.

Because the development is being fast-tracked away from state-provided infrastructure and is outside the government’s planned development areas, the developer will need to meet much of the local infrastructure needs via a voluntary planning agreement, which is usually funded by levies on new lots.

Sharpe told Guardian Australia on Monday: “The CPCP is a complex plan that we need to get right. I am working through the issues to ensure that we protect koalas and the rest of the stated conservation outcomes of the plan.”

“The rezoning of land at Appin will provide for the much-needed additional 13,000 homes while reserving more than a third of the site for environmental and koala protection,” planning minister Paul Scully said.