European Commissioner Mairead McGuinness has said that for some member states who are using "dirty coal", the transition to renewable energy is "not going to be a one-step process".
Speaking on RTÉ's Today with Claire Byrne, the European Commissioner for Financial Services, Financial Stability and the Capital Markets Union said they see a role for gas in the transition towards cleaner energy sources.
It follows controversy over a draft proposal to classify nuclear and natural gas energy as 'green for investment purposes', which has been dubbed 'greenwashing' by some.
"The devil if you like is in the detail of our proposals, where we're saying that gas is not given a green card, as is suggested," she said.
"But rather, a term when it can be used and in time will have to be replaced by low carbon gasses.
"When it comes to nuclear, we already have over 100 nuclear plants operating in Europe.
"For many member states it is an important low carbon energy source and we wanted to provide for the possibility of investment in nuclear - again, with very strict conditions, so nuclear and gas are not seen as long-term energy sources but rather as a bridge towards achieving climate neutrality."
Ms McGuinness said there are "many different views" about gas and nuclear, and that gas is for member states who will be replacing dirty coal facilities and "moving towards a cleaner, greener solution".
She said there are "very detailed" lists in their proposal of what the nuclear sector needs to do in terms of waste management and finding solutions for the 1% of waste which is "problematic".
"Today if you look at the nuclear sector, 26% of the European Union's electricity comes from the nuclear sector," she said.
"So it is significant and it cannot be switched off overnight, but it can over time."
Ms McGuinness said they need to keep on the lights, but they also need to be climate neutral by 2050.
She said they believe that their proposal, which is out for consultation, will help them meet that objective.
She said that when you read the detail of the proposal it is clear that they are "not locking in" any technology that they regard as transitional.
She said she is "very aware" that some member states are against nuclear power and the arguments around gas.
She said they are "not giving a free card" to either gas or nuclear, and are putting strict conditions as to how they can be regarded as sustainable in transition.
"The arguments are divisive but I'm very clear about my role as Financial Services Commissioner," she said.
"That is to give the financial markets clarity, to give signals around sustainable economic activity, and to give leadership and transparency.
"On all of those fronts, our proposal is clear and focused. Of course it's controversial and we will now listen and engage with stakeholders in this consultation period."
