A Labour spokesperson said: "Kemi Badenoch claims she's ready to 'deal with reality' while remaining in complete denial about the reality of the Tories' appalling record in government.
"The Tory leader's position is at odds with her own historic views. In government, she openly championed net zero.
"It's clear the Conservatives stand for nothing and have learned absolutely no lessons. They haven't changed."
The Liberal Democrats said Badenoch was "taking a leaf straight out of Nigel Farage's playbook".
"Scrapping net zero and renewable energy targets will simply increase our reliance on foreign fossil fuels," the party's deputy leader Daisy Cooper said.
As a minister, Badenoch promoted the 2050 target as "crucial" to "achieve a cleaner, green future".
Some Conservative voices criticised her latest move.
Sam Hall, Director of the Conservative Environment Network, called it a "mistake" and argued Badenoch's speech "undermines the significant environmental legacy of successive Conservative governments".
He said Badenoch was right to criticise Labour's approach, but argued "the net zero target is driven not by optimism but by scientific reality; without it climate change impacts and costs will continue to worsen".
But Lord Craig Mackinlay, a Conservative peer and net zero sceptic, praised Badenoch's "reality check" on the 2050 target.
"Most of the world has already given up any pretence that it is affordable or achievable," he added.
"Intermittent renewables that only stack up on the back of buckets of taxpayer cash are not the answer when we need cheap, reliable and secure energy."