Environmental Earth Sciences chief executive Phil Mulvey told a conference in Singleton recently that more than 100 mining leases have yet to be surrendered to state governments because of inadequate remediation at the mine's closure.

"The main environmental issues that prevent the surrender of [a] mine lease at closure relate to the placement of mine waste, the waste's interaction with water, and colonisation by invasive weeds," he said.

"The mine companies are not reaching the environmental benchmarks, and the state agencies are refusing to take back the land."

But the NSW Minerals Council disputed Mr Mulvey's claim.

Council chief executive Nikki Williams said more than $1.1 billion had been lodged in environmental security deposits with the NSW government.

"These security deposits ensure that taxpayers are not left with any rehabilitation liability if it is not carried out to agreed standards," she said.

The council cited examples of former Hunter mines where security bonds had been partly or wholly returned following rehabilitation.

They include New Wallsend Colliery and Great Greta Colliery.

"Rehabilitation is carried out during mining to minimise the total amount of land disturbed by a project," Dr Williams said.

Mr Mulvey agreed some mine sites had been well rehabilitated but called for improved collection of data during the mining process.