The prime minister was interested in LDA's involvement in the Swansea Bay Tidal Lagoon project- which will be the world's first tidal energy lagoon.
A tidal energy lagoon is a harbour-type structure that sees a tidal sea area closed off and hydro turbines installed in the sea to generate electricity.
LDA Design is the masterplanner and lead consultant for the project - which was submitted for planning approval earlier this year.
Work on the lagoon site is expected to start in spring 2015 - subject to approval of the Development Consent Order (DCO) application.
Partner at LDA Design's Oxfordshire office Alister Kratt and chief executive officer of Developer Tidal Lagoon Power Mark Shorrock discussed the Swansea Bay Tidal Lagoon project in depth with the Prime Minister- showing him a 3D model of the masterplan.
Kratt said: "The government is clearly focused on increasing and delivering energy and infrastructure projects in the UK. We welcomed the opportunity to speak with the Prime Minister about our work on Swansea Bay Tidal Lagoon."
He aded: "As an exemplar project, it will not only help regenerate the area through the opportunities that our masterplan provides, it will also help hit 495 GWh per annum, enough energy to power 155,000 homes."