A former Tory cabinet minister is backing efforts to force through tough green laws after Brexit, amid anger over plans that would weaken environmental protections once Britain leaves the European Union.

Four former environment and climate change secretaries from three parties told the Observer they had concerns about “toothless” plans announced by the government last week, which suggested the new post-Brexit green watchdog would lack the power to take the government to court.

Senior Tory MPs are also said to have concerns about the move. It comes after a row over post-Brexit green laws between Michael Gove, the environment secretary, and the chancellor, Philip Hammond.

Gove, a leading Brexiter, has been keen for the new watchdog to have identical powers to those currently enjoyed by the European commission, which can fine governments that fail to meet their green obligations. However, the Treasury is said to have concerns about the impact on post-Brexit growth and construction.

A cross-party group of peers is planning a rebellion this week that would keep all the green protections currently in place, including the power to take legal action against the government.

‘The government committed itself to putting into British law all the protections and commitments that we have in the EU’: John Selwyn Gummer, Lord Deben. Photograph: Eamonn McCabe/The Guardian

Among those backing the rebellion is John Gummer, now Lord Deben, the former Tory environment secretary and current chairman of the UK committee on climate change. “The government has moved significantly on this, but the new watchdog has got to have the power that we now have as members of the European Union – to call the government to account,” he said. “There is no such power in the current consultation document.

“We wouldn’t have had any of the action that we’ve had up until now unless the EU structures had the power to hold the government to account. The government committed itself to putting into British law all the protections and commitments that we have in the EU. Unless we make these changes, you don’t do that.”

Green groups immediately spoke out after Gove’s “Green Brexit” consultation, published last week, contained no commitment to give the new watchdog power to initiate legal action. It suggested it would have the power only to issue advisory notices. However, there is still time for the watchdog’s remit to be strengthened before its formation.

Former climate change secretaries called for an urgent rethink. Labour’s Ed Miliband said: “Climate change is the biggest environmental challenge the world faces but these proposals for a weak regulator with no proper legal powers are yet more evidence of the government’s continued failure to match their rhetoric with action.

Gove’s watchdog is a toothless mutt Chris Huhne, former climate change secretary

“Michael Gove claimed to have been deeply moved by David Attenborough’s Blue Planet. But his watchdog is about as toothless as a jellyfish.”

The Lib Dem MP Ed Davey, who served as climate change secretary under the coalition government, said the post-Brexit plans would leave Britain with “a weaker environmental regime than Trump’s America”. He added: “Before we joined the EU, we were called the dirty man of Europe. We cleaned up our act during our membership. Over time, Britain has become one of the champions of environmental legislation. This will completely damage that reputation. The threat is we will go back to being the dirty man of Europe once again.”

Chris Huhne, who also held the role under the coalition, said: “Gove’s watchdog is a toothless mutt. Basic legal principles in EU law like polluter pays and the precautionary principle have been ditched to allow a sludge brown not green Brexit.”

Amy Mount, of the Greener UK coalition, said: “The government’s plans for this toothless watchdog would leave us with weaker protections after Brexit. The power to take the government to court is a strong deterrent and then a vital last resort when the law is not being followed. This means we need more than advisory notices if our air is dangerously polluted, or wildlife under serious threat.

“It is also very troubling that the watchdog will not enforce law relating to climate change, despite ministers’ claims of global leadership on this urgent challenge. Bizarrely, this would mean that after Brexit the climate will be less protected than every other aspect of our environment.

“There is still time for the government to live up to its stated ‘world leading’ ambitions, but time is fast running out.”