A new port for Essex has been given formal consent by the Secretary of State for Transport.
Tilbury2 will be built on brownfield land next to the Port of Tilbury, in Thurrock.
Forth Ports Group's £1bn investment programme would see the volume of cargo handled at the Essex site double from 16m to 32m tonnes.
The company said the new terminal would be "fit for purpose for the UK's departure from the EU".
It added that Tilbury2 would embrace the latest technologies and streamline the border process.
Construction of the expansion is scheduled to start on 13 March with the intention to be operational by Spring 2020.
Tilbury2 will be the UK's largest unaccompanied ferry port and the country's biggest construction processing hub, according to its owners.
Forth Ports Group said expansion was essential at Tilbury to cope with rising demand for construction materials and aggregates from Britain's construction sector, and imported and exported cars.
A Port of Tilbury spokeswoman said it had seen an increase in commercial ferry traffic, which carries consumer goods, perishables (food and drink) and steel between Europe and the UK.
But environmental groups are concerned over the impact on wildlife and also on Tilbury Fort, which sits between the existing port and the planned site of the expansion.
Buglife said the decision to expand simply added to an "insect catastrophe".
The group is calling on Natural England to declare the brownfield site an area of scientific special interest.
"Unless Natural England step up and fulfil their duty to protect our best wildlife sites, we are going to continue to lose our precious invertebrate species," said its spokesman.
"The former Tilbury Power Station site supports at least 1,397 species of invertebrate, among them 159 species of conservation importance and 31 which are rare or threatened."
Aidan Lonergan of Natural England said it was aware of the importance of wildlife on this site and would "work closely with developers to understand the challenges and opportunities posed by these plans."
Charles Hammond, Chief Executive of Forth Ports Group and owners of Tilbury Port, said: "This is great news for the UK at a time when the country needs its ports more than ever before.
"Tilbury2 will deliver much needed port capacity to support businesses importing and exporting to and from Europe and the rest of the world."
As well as a roll on/roll off ferry terminal for importing and exporting containers and trailers to northern Europe, Tilbury2 will also have a rail terminal to accommodate the longest freight trains of 775m.
A new deep-sea jetty will be provided and the the port area will increase from 383 hectares to some 445 hectares.
The group added it believed jobs would increase from 3,500 to 12,000 in the next 10 to 15 years.
Objectors to the new port have six weeks to file a claim for a judicial review of the government's decision.