The fourth multi-deck vehicle terminal has been built to meet a surge in demand for the export of British built cars through the port, particularly to China and the US.
Dock owners Associated British Ports (ABP) also today announced today a further £7.5m investment to build a fifth vehicle terminal at the eastern docks.
The port is expected to handle around 700,000 vehicles this year, up from 518,000 in 2011, with BMW, Jaguar Land Rover and Honda the leading exporters of vehicles through Southampton.
Mr Cable said: "The British car industry is a great success story and our increasing exports are proving a boon for the port of Southampton - the opening of a new vehicle terminal along with provisional funding from the regional growth fund for the city of Southampton’s infrastructure will allow further growth for the future.”
Mr Cable was joined by ABP port director Doug Morrison and car manufacturer bosses to unveil a plaque naming the new four-storey Atlantic Vehicle Terminal, which will store more than 9,000 vehicles.
Mr Morrison is also chairman of the Solent Local Enterprise Partnership, the body now tasked will promoting economic growth in the region.
The Solent LEP has been awarded £2.1m from the Government’s regional growth fund to provide micro-finance and small Business grants of up to £100,000 to create new start-ups, and allow existing companies to grow.
And Southampton City Council, backed by the LEP, has won a £5.6m bid to build a has new dual carriageway along Platform Road to ease motorists’ congestion misery and pave the way for an expansion of Southampton’s port and cruise operation.
The new Daedalus Enterprise Zone, a former MOD base near Gosport, has also been awarded £3 million from the fund to support up to 20 businesses.
The airfield is set to be turned into a marine and aviation hub, which could create up to 3,700 jobs by 2026.
Businesses that decide to invest there could benefit from discounted rates and superfast broadband. It is expected between 38 and 45 businesses will set up there initially, with permission for 164 new homes.
As part of his visit to Southampton, Vince Cable was also visiting Griffon Hoverwork in Woolston, a leading manufacturing and exporter of hovercraft.
Mr Cable said: “The work of Griffon Hoverwork also highlights the value of a skilled workforce including local apprentices and undergraduates who are employed across a range of different disciplines.
"As they have shown, British manufacturing has a big role to play in exporting to international markets.