Nadia Whittome, the Labour MP for Nottingham East, said she found it especially frustrating that an MP – who she said was from a generation and socioeconomic background that was most responsible but least affected by climate change – was happy to crack jokes.
"The flippancy is really, really jarring," she told Yahoo News UK.
"I overheard a Tory behind me after a debate on COP saying: 'Yeah, yeah, we get it. The world’s burning!' – and he was joking about it."
The climate change summit, which was held in Glasgow this year, saw almost 200 nations sign up to commitments to curb climate change.
Whittome said she heard the comment ahead of a debate about COP26 in October, shortly before the conference started.
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"It's my generation who are going to be saddled with the consequence says of the system that you and and your generation in your class has allowed to happen," she said.
"So forgive us for being angry and demanding change of our lawmakers.”
Speakers at COP26 warned it is highly likely that people currently aged 30 and below would experience some of the most catastrophic consequences of climate change.
A recent YouGov poll found that 72% of people age 18-24 were either very frightened (26%) or fairly frightened (46%) of the impacts of climate change.
Whittome expressed her concern about what she perceived as a lack of progress at the COP26 summit.
"There was nowhere near enough progress to avoid climate disaster," she said.
"It fails on both the science and climate justice. From the outset, COP was set to produce disappointing results, wasn’t it?"
She added: "There [were] some good things. There was an increased financial commitment from wealthy countries to those most affected: that’s for adaptation that was agreed in the final text.
"But that’s still not enough to to provide all of the adaptation measures required, and the loss and damage fund only stands currently at £2m, which isn’t going to go very far. ”
Whittome participated in protests outside COP26 led by activist Greta Thunberg.
"I was on both of the the big rallies, on the second day marching with green New Deal Rising," she said.
Whittome added that she is also a member of the environmental audit committee, and says she sees her role in parliament as a responsibility to achieve lasting change.
"I see my role as being to amplify the demands of the movement inside the establishment," she said.
COP26 – which officially ran from 31 October to 12 November, though negotiations went on longer – has been been widely criticised for not going far enough.
A particular sticking point was when the final document was amended by China and India to "phase down" coal usage rather than "phase out".
While some supporters of the agreement say it is an important milestone, because it is the first time such reference has been included, others say that it is a death sentence for small island nations at risk of being wiped out by rising sea levels.
COP26 president and Tory MP Alok Sharma appeared to be on the verge of tears as the conference drew to a close, and later said: "China and India will have to explain themselves and what they did to the most climate-vulnerable countries in the world."
Watch: 5 takeaways from the Glasgow climate change conference