It will be the successor to the Royal Yacht Britannia, which retired in 1997 after 44 years of service.
But the proposed yacht has proved controversial, with senior Tory peer Ken Clarke branding it a “complete waste of time” and “silly popilist nonsense”.
So, what are the plans for the yacht, how much will it cost - and why has there been backlash?
Here is everything you need to know.
What are the plans for the new national yacht?
The new yacht will be commissioned by the UK Government in an effort to boost British trade.
It is hoped that the ship, which will be part of and crewed by the Royal Navy, will improve global industry, as well as boosting trade, jobs and growth.
Mr Johnson wants the new vessel to promote British interests worldwide, including hosting trade talks and diplomatic meetings while the UK looks to build post-Brexit relationships.
Speaking last month, the Prime Minister said the national flagship would highlight the UK’s “burgeoning status as a great, independent maritime trading nation.
He added: “Every aspect… from its build to the businesses it showcases onboard will represent and promote the best of British – a clear and powerful symbol of our commitment to be an active player on the world stage.”
It is thought British businesses will be able to promote their products on the vessel.
The name of the new flagship is yet to be announced, although there have been reports the ship will be named after the Duke of Edinburgh, who passed away in April 2021.
The tendering process for the ship’s design and construction is to begin soon, with the Prime Minister’s official spokesperson saying Mr Johnson wants the vessel to be built in the UK.
And there will be an emphasis on using the latest green technology, Downing Street said.
Construction on the vessel could start as early as next year, with the ship expected to begin service within the next four.
It could then be in service for about 30 years.
How much will the ship cost?
The trade ship is reportedly set to cost £200million, and will be paid for out of the Ministry of Defence’s (MoD) budget.
But costs for the construction and operation of the new vessel will not be confirmed until after the tendering process has concluded.
"This new national flagship will boost British trade and drive investment into the economy," the Prime Minister’s official spokesman said on Monday (21 June).
"The procurement process, which is being done through the MoD, will reflect its wide-ranging use and so it will be funded through the MoD, as set out previously."
Asked why the funding for the ship would come out of the MoD’s budget, when the yacht will be classed as a trade ship rather than a military vessel, the spokesman said that Defence Secretary Ben Wallace had responsibility for UK shipbuilding.
And he declined to comment on where the MoD would find the reported multi-million pound cost required for the project out of its budget.
Labour has previously called on the government to clearly set out how the ship would boost trade and jobs in Britain and has urged it to “focus on value for money” with regards to the project.
Why is it controversial?
The project is controversial, with former Conservative Chancellor Ken Clarke dismissing the plans for the new yacht as a “complete waste of time”.
The senior Tory peer urged the government to show “restraint” when it comes to public spending on Tuesday (22 June).
Asked whether the project was a good use of taxpayers’ money, Lord Clarke told BBC Radio 4’s Today programme: “Complete waste of time — silly populist nonsense.
“£200 million is not going to cause problems, but it shows there are people in No 10 who just think there’s free money, who think that waving a Union Jack and sending yachts and aircraft carriers around the world shows what a great power we are, we’ve no money for that kind of thing.”
The former Tory MP added that the government needed money to “actually improve the quality and availability of social care”.
His comments came as a top naval architect said the vision for the new national yacht looked like a “1950s fishing trawler”.
Stephen Payne, the designer of the impressive ocean liner Queen Mary 2, told the Daily Telegraph it would make a “very poor” flagship for the UK.
He also cast doubt on whether the proposed vessel would earn the approval of the Royal Navy, adding: “They say they'll use a Royal Navy crew. Isn't there a chronic manpower shortage within the service? Will the Navy look at this new vessel not with adoring eyes but with despair as it struggles to keep frontline ships at sea?
"As for financing this ship, there's £200 million to find and I'd be surprised if the running costs weren't £5 million a year."
On Tuesday morning, Health Secretary Matt Hancock defended the yacht and claimed it was “great value for money” when asked if the finances being earmarked for the project should be spent elsewhere.
He said: “It’s a brilliant idea because it’s how we can help to sell Britain abroad. You only need to encourage a small amount of trade in order to pay for a yacht like this over and over again.”