Natural gas and nuclear energy have been temporarily excluded from the European Union's list of green investments.
The investment programme aims to improve the flow of money towards environmentally sustainable economic activities across the continent.
The Commission announced new measures on Wednesday for its green taxonomy: a classification system designed to help scale up sustainable investment and to further implement the European Green Deal. But it neither included nor exclude gas or nuclear from the criteria.
Speaking to Euronews after the presentation in Brussels, Commissioner for Financial Services Mairead McGuinness said more time was needed to reach a decision on so-called "transition" energies like gas.
"There are many countries with coal at the moment that need to make that big jump, and gas plays a role," McGuinness said. "The taxonomy regulation in itself...is quite restrictive, so what we will do is to look at the role of gas in a wider element of transition.
"I think what we learned from this experience is the real desire from member states to be on a path towards climate neutrality, but also an understanding of how difficult that is."
Under pressure from countries in eastern Europe to make gas a transition energy, the Commission said complementary measures will follow later this year.
But Dutch Green MEP Bas Eickhout told Euronews that although there is some room for transition energies, Europe should not be investing heavily in them.
"If Europe is saying that on one hand we want to be climate neutral in 30 years time, it is ridiculous to say, at the same time that we can also call building a new gas fire powered plant a green investment.
"It will be there for 40 years at least, and then we will be over the 2050 deadline when we should have become climate-neutral. So, I am not saying there is no role for gas, but it is very limited."
Brussels also says it is currently still undecided whether or not nuclear energy is to be considered a green investment either.
The French government is pushing for nuclear to be recognised, with the country's finance minister, Bruno Le Maire previously saying: "France will advocate that nuclear energy should be part of this eco-label."
Greenpeace has described the bloc's new rules as being "greenwashed".