The Paris agreement, which recently came into force, commits countries, including EU member states, to comply with strict limits on CO2 emissions in the fight against climate change.
GUE/NGL group MEP Estefanía Torres Martínez said, "The election of Donald Trump is a tragedy for the planet. His attitude is not surprising given that he denies the mere existence of climate change.
"While countries like Japan are setting ambitious targets to cut carbon emissions by 26 per cent others express the intention to break their commitments with total impunity."
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Torres was in Marrakech this week as part of the official delegation of the European Parliament attending the COP22 climate summit.
Speaking from Morocco, she said, "This possible backtrack by the United States poses many questions, such as the relevance of signed agreements and binding commitments between countries. There is a risk to render the emissions agreements of little utility."
Torres added that "it is now up to the EU to fight for a just energy transition."
She said it has "become clear" at the summit that China's position is softening and that, together with the EU, there are "opportunities" to influence developed countries.
Her comments come after environmental group Climate Action Network (CAN) said this week that Trump could jeopardise funding to fight disasters in developing countries.
Torres believes that it is necessary "to be prepared, since it is expected that 2017 will be a year of new temperature records with the poorest people the hardest hit.
"It is natural that for a billionaire like Donald Trump this is not a concern," the Spanish MEP argued.
"When we talk about climate change, we also talk about hunger and poverty. We speak about political will to eradicate them or to remain accomplices to this unjust system.
"These summits won't serve their purpose unless we stand up to these challenges and fight against unelected petrol companies that want to co-opt these spaces," Torres said.
On 30 November, just a few days after COP22 finishes, the European Commission will publish its so-called "winter package" consisting of eight legislative proposals.
This includes a revision of the renewable energy directive, the energy efficiency directive and the rules designing the European electricity market.
Campaigners say that draft documents which were leaked on Tuesday indicate that the EU, in "stark contradiction" to the objectives of the Paris agreement, is planning to water down its energy policies after 2020.
Jean-François Fauconnier, Renewables Policy Coordinator at Climate Action Network (CAN) Europe said, "Renewables would also lose the right to get priority over other, polluting energy sources in terms of access to the European electricity grids.
"At the same time the proposals keeps the gate open for member states to subsidise the use of coal for power generation under the guise of so called capacity mechanisms."
He went on, "The proposals are miles away from what is needed to turn the Paris agreement goals into reality. A low target and lenient rules will not give European households and companies the confidence to invest in the renewable future.
"If European Commission President Jean-Claude Juncker is serious about fulfilling his promise to make the EU 'number one in renewable energy', the leaked proposals need to be substantially improved before they are published."