Lake says his contract negotiations were more with Ospreys than the WRU.
"They're [Ospreys] not really sure about what kind of position they're going to be in next year either," said Lake.
"I know it was very tough for them to be able to put contracts on the table with everything that is going on.
"It's not an easy decision, but it's one that I feel I've got to take."
Lake says he did not take the decision to leave Ospreys lightly.
"It was a tough decision because you never want to leave the club you started out at," said Lake.
"The staff and the boys are always the toughest things to leave. We've got a good group of boys that I've been with since I came through.
"The coaches as well, a lot of them were my coaches at Under-18 level.
"That's the hard bit to leave. The people that you form good bonds and friendships with. The fans as well have been class over the years, too."
Lake says he is looking forward to play in the English Prem.
"Very excited, it's an exciting league, a big league," Lake said.
"It is a new opportunity for me, leaving a place where I'm comfortable and going out of my comfort zone a bit to test myself in a new league and a new environment.
"I'm excited, but not ready to go just yet."