The environment department say it’s too premature to discuss what federal powers could be given to states under the “one-stop shop” policy.

The Queensland government could be given power to assess the impact of uranium mines in the state under proposed federal changes to environmental approvals.

The revelation emerged on Monday as the environment department was grilled by opposition and Greens senators about the federal government’s plan to create a “one-stop-shop” for environmental approvals.

The Queensland and NSW governments have signed a memorandum of understanding (MoU) with the Abbott government over the plan, which aims to deliver faster approvals and eliminate regulatory duplication.

Opposition to the policy has been fierce, with critics claiming it will erode crucial environmental protections by handing federal powers to the states.

Australian Greens senator Larissa Waters on Monday quizzed officials from the environment department about whether the Commonwealth would retain power over nuclear activity under the proposed changes.

She said Environment Minister Greg Hunt had previously indicated nuclear activity would be “quarantined” under the changes, and asked if this was still the case.

Newly appointed department secretary Gordon de Brouwer told a Senate estimates committee that nuclear activity was “approved by the Commonwealth minister, and assessed under this agreement by the state”.

“So this does give away the assessment of uranium mining to Queensland?” Senator Waters asked about the proposed agreements.

“Yes, it allows the state to undertake those assessments, subject to the agreement,” Mr de Brouwer replied.

The Newman government wants to begin assessing uranium mining applications from mid-next year after lifting a longstanding ban.

The state has about $10 billion worth of reserves, including $8 billion in the northwest.

Mr de Brouwer stressed both Prime Minister Tony Abbott and Environment Minister Greg Hunt had been “very firm” that standards under the Environment Protection and Biodiversity Conservation Act would be maintained.

First assistant secretary Dr Rachel Bacon said it was too premature to discuss what exact processes would be handed to the states, as the deals were still under negotiation.

But the policy position was to “pursue as comprehensive approach as possible” when it came to accrediting the states, she added.

Greens senator Scott Ludlum asked what purpose the environment minister would serve if these deals went ahead and his responsibilities were handed to the states.

“In order to cut red and green tape and simplify the process … and still maintain environmental standards at the high level they have been in the past,” said Senator Mathias Cormann, acting on behalf of the environment minister.