The city's Lib Dem Council Leader has written to the Prime Minister asking that the new national flagship yacht be based in Portsmouth.
The planned vessel, which has not yet been named, will be the successor to the Royal Yacht Britannia.
In a letter to the government, Portsmouth City Council leader Gerald Vernon-Jackson said the ship should be based in the 'home of the Royal Navy'.
The Liberal Democrat said the city's proximity to London made it ideal for royal and ministerial visits.
The vessel will be the first national flagship since HMS Britannia was decommissioned in 1997 after 44 years' service.
Crewed by the Royal Navy, it will be a ship rather than a luxury yacht and is aimed at promoting trade.
Writing to Prime Minister Boris Johnson, Councillor Vernon-Jackson said: "Portsmouth is the home of the Royal Navy and this new ship will be a naval ship.
"My understanding is that this new ship will be used by ministers, members of the royal family and leading industrialists to showcase the UK around the world.
"Of all the three naval bases in the UK, Portsmouth is the closest to London and therefore allows easier access for the people who will be using this new ship."
Boris Johnson gave details in May of plans for the ship, which will be used for hosting events like trade fairs and diplomatic meetings. The 'floating embassy' could cost the government between £200m and £250m and would be completed by 2024 at the earliest.