A new watchdog supposed to safeguard the UK’s environment after Brexit will lack the legal “teeth” necessary to hold the government to account, the country’s top lawyers have said.

According to the Bar Council, the body to be charged with overseeing the UK’s environmental protections would not be able to take the government to court, a key power under the current legislation which comes from the EU.

That would leave the watchdog without “teeth”, said the Bar Council, which represents the UK’s barristers, and would not replicate the current legal framework for safeguarding key issues from air and water quality to biodiversity.

Celina Colquhoun, of the Bar Council’s law reform committee, said: “[We are] concerned that the proposed powers for the new environmental watchdog do not go far enough. It would not have comparable powers to the EU commission in respect of complaints by individuals, and there is no proposed role or power for the body to take the government to court.”

That could severely curtail the ability of activists to stop dangerous breaches of safe levels of pollution, and other environmental harms. For instance, only by dint of repeated legal actions stretching to the UK’s high court and the European court of justice have campaigners been able to force ministers to take action on air pollution. That could become impossible after Brexit, as the proposed new watchdog won’t replicate the role the courts currently have.

As part of the Brexit process, ministers have pledged that new legislation would offer environmental protections equivalent to those the UK has under EU law. The proposals for a new watchdog that would oversee the UK’s natural environment and enforce regulations are a key plank of that strategy.

But the draft proposals are too weak in legal terms to achieve that, the Bar Council warned on Tuesday. In its response to the government’s ongoing consultation, the organisation – which represents the UK’s top lawyers – found serious weaknesses in the government’s plans.

Campaigners have previously raised concerns, but this is the first time the country’s top lawyers have weighed into the debate.

The Bar Council wrote: “[We] consider that the new body – as currently proposed – would lack equivalent powers to those currently available to the [European] Commission and other related legal bodies. [We are] therefore concerned that there is an absence of powers that have any real force or ‘teeth’.”

For the last 40 years, most changes to environmental regulations – on air pollution, water quality, habitats and biodiversity – have come through EU directives. As a result, green campaigners were among those most concerned about the effects of Brexit.

The prime minister, Theresa May, moved swiftly to allay such fears, putting forward early this year a 25-year environment plan with the promise to “make ours the first generation to leave the natural environment in a better state than we found it”.

Colquhoun added that the new watchdog would also “need to have a proper role in securing compliance with international environmental agreements”. Climate change is specifically excluded from the watchdog’s role, as the Committee on Climate Change is supposed to fulfil that function, but it still leaves other international standards to be determined.

A Defra spokesperson said: “These claims are erroneous. We have confirmed that the new independent environmental body will be able to bring legal proceedings against the government if it considers the government is not complying with environmental law. This commitment is now enshrined in law. We will publish legislation to give the body this power in draft later this autumn.

“We are committed to a green Brexit where environmental protections are not only maintained but enhanced.”