Theresa May suggested companies that invested in the UK because it was part of the EU would leave in the event of Brexit, in a private speech she made to banking firm Goldman Sachs.
The Prime Minister, who at the time of the speech was home secretary, outlined economic benefits and security concerns as among the reasons the UK would be better off remaining in Europe, a recording leaked to The Guardian reveals.
"I think the economic arguments are clear," she said during the 26 May talk at the investment bank in London.
"I think being part of a 500-million trading bloc is significant for us. I think, as I was saying to you a little earlier, that one of the issues is that a lot of people will invest here in the UK because it is the UK in Europe," she added.
"If we were not in Europe, I think there would be firms and companies who would be looking to say, do they need to develop a mainland Europe presence rather than a UK presence? So I think there are definite benefits for us in economic terms."
May's Goldman Sachs talk appears to reveal that she was perhaps personally more invested in remaining in the UK, with her private comments going further into detail on the topic than she had previously said in public.
During the lead-up to the EU referendum, May campaigned to remain in the EU, as per the government's position on the topic, but was not one of the loudest voices in the fray.
However, on becoming the leader of the Conservative Party, she reassured those who had voted in favour of leaving the EU that "Brexit means Brexit", and has since reiterated she does not intend to backtrack on this promise.
On 21 October, May met with European Commission president Jean-Claude Juncker, and is working towards negotiating a deal for the UK that she has promised will include a cut on EU immigration, amid warnings from the leaders of other EU countries against a 'hard' Brexit.