The Speaker of the House of Commons gave the green light for the DUP to be called "dinosaurs" ruling it was not "unparliamentary language".
It happened during the Queen's Speech debate on Wednesday.
Green MP Caroline Lucas questioned Prime Minister Theresa May on the absence of environmental policies and asked if she had been influenced by her new political allies as discussions continue between the DUP and the Conservative Party.
She said: “It’s good to see her (Theresa May) facing the other parties and that she has actually turned up - which was not always the case in the election campaign.
“The gracious speech contained eight Brexit bills, but not one single one of those covered the environment.
“Is her failure to propose a Brexit bill on the greatest challenge that we face because she simply doesn’t care about the environment and climate change, or because she’s been influenced by the DUP dinosaurs who sit beside me and don’t want to take that kind of leadership in the future?”
As Theresa May began her answer, DUP MP Jeffrey Donaldson raised an immediate point order to the objection of the use of language.
He said: "Is it parliamentary for the honourable lady to describe us in the unparliamentary terms that she did, which I regret? She does not understand the policy that my party has on the environment. She should go and read our manifesto. We have the right to speak for the people of Northern Ireland."
However the Speaker John Bercow said: "The use of the word in question is not unparliamentary, it’s a matter of taste as to its desirability.
"The word in question refers to a species that survived for many millions of years."
The DUP have been criticised after their 2017 manifesto did not mention climate change or the environment.
Previously, MP Sammy Wilson, as Environment Minister said he believed man-made climate change was a con.