The international trade secretary, Liam Fox, has been forced to clarify comments suggesting individuals could question the scientific consensus on climate change.

Speaking in the Commons after protesters from Extinction Rebellion held protests across the City of London, Fox suggested even those who did not accept that climate change was man-made should still seek to manage the planet’s resources.

“It’s important that we take climate issues seriously,” Fox said. “Whether or not individuals accept the current scientific consensus on the causes of climate change, it is sensible for everyone to use finite resources in a responsible way.”

Both Labour and the Lib Dems said the comments were shameful and amounted to excusing climate change denial.

Barry Gardiner, the shadow international trade secretary, said Fox was “showing confusion and ignorance on such a staggering scale”.

“The government needs to act with the urgency that the science demands, not provide weasel excuses for climate deniers. It is just not acceptable behaviour from a cabinet minister.”

Wera Hobhouse, the Lib Dems’ climate change spokeswoman, described the government as “apologists for climate change denial” and said it could not be debated.

“In a week where protesters have filled the streets of London and activist Greta Thunberg has visited parliament, it is outrageous that Liam Fox is now legitimising those who deny climate change,” she said.

“Climate change is happening. It is a scientific fact, not an opinion to be argued about. Comments like this show the Tories clearly cannot be trusted to take it seriously.”

Fox later clarified the comments in a tweet, saying: “I have always taken environmental issues extremely seriously. The state of our planet should concern us all. There is a clear scientific consensus on climate change, which I fully respect. Even those who don’t accept it should want to see our finite resources carefully managed.”

About 400 activists have been halting traffic and several attached themselves to the London Stock Exchange, on what the group said would be the final day of protests intended to highlight the role of the finance industry in fuelling climate change.

On Wednesday, the London protesters agreed to remove blockades and campsites at Marble Arch and Parliament Square and said they had ignited a conversation that would go far beyond the protest sites.

The environment secretary, Michael Gove, is understood to have agreed to meet representatives of the group, though an Extinction Rebellion spokesman said that was not connected to its decision to end the current protests.