Seems more like lack of leadership than leadership conflicts.
Getting attached to specific roles in this kind of situation isn't the best solution. I'd look for leadership among the project team, and wouldn't care whether one's title is PM or tech lead or whatever. If I found the person I'd give them power to make project-related decisions and support those decisions, as otherwise it would ruin their authority.
Another thing to do is clearly setting up responsibilities. Who does what. Who is responsible for what. Again, I wouldn't care much about who should do what basing purely on their title - I'd look more for people who genuinely care about quality/scope/budget/client satisfaction/you name it.
If you have a good meeting facilitator at hand, possibly not someone from the team, you can also run a meeting where you try to call all the issues, possibly solve them or set solutions to avoid them in future to improve cooperation within project team. In other words run a project retrospective now. But if you don't have an arbiter it may get out of control and become more of a flame than constructive discussion.
If above doesn't work you may want to refer to formal responsibilities, e.g. PM should do this, this and that and if they don't management should take care about that. However as long as I don't have to I wouldn't go for that as it would only make personal conflicts more intensive. Another step is asking for changes in project team - finding anyone with strong leadership skills to join the team (or get exchanged for someone from the current team) and informally take the sinking ship over.