The backers of a new national flagship to be used by the royal family are to launch a public appeal for funds after they decided against seeking government money.

The £80m project originated as a replacement for the Royal Yacht Britannia and has won the private backing of the Queen and Prince Philip, according to project insiders; but construction is to be funded by members of the public and corporate sponsors.

The proposed 157m-sailing ship is to double as both a training vessel for young people and secure accommodation for members of the royal family when they are abroad.

The charity behind the project, Future Ship Project 21st Century, said it hopes public interest around the Queen's diamond jubilee celebrations in June will help fill the project's coffers.

The prospect of a vessel designed in part to host the royals being funded by the public at a time of austerity could cause political embarrassment, and Downing Street has been quick to say there will be no government money for the project, despite the suggestion by the education secretary, Michael Gove, that might be a possibility.

Buckingham Palace declined to comment on whether it approved of public fundraising for a ship to be used by the royal family or if the palace would contribute.

"The Queen's office is aware of the project's existence," a palace aide said. "We are also aware that the prime minister has sent a message of support for the initiative to the project organisers."

Leading British companies will also be asked to donate funds in exchange for naming rights to various decks and facilities on board. Companies listed in the FTSE 100 will be approached, said Rear Admiral David Bawtree, chairman of the FSP21 consortium, leaving open the possibility that firms from British American Tobacco to Marks and Spencer could be asked to contribute to the royal vessel.

So far two unnamed Canadian businessmen have pledged a possible £10m, but there are no other firm offers as yet.

"We will go for national fundraising and I hope that members of the public will contribute to this," said Bawtree.

"People will support this, as I have seen when I have given talks about the project. The jubilee also lends itself to a national appeal."

As well as Bawtree, a former commander of the Portsmouth naval base, the project organisers include Colonel John Blashford-Snell, who in 1968 organised the first descent of the Blue Nile at the request of Haile Selassie, the emperor of Ethiopia, and Maldwin Drummond, a past Commodore of the Royal Yacht Squadron. They intend to invite 220 young people on board for three-month training voyages and also use the ship for environmental surveys.

The decision to launch a national appeal comes after David Cameron gave his backing for the project, a key step in securing commercial sponsorship. David Willetts, the universities minister, had written to the prime minister urging him to support the four-sail ship after he was lobbied by Bawtree.

Gove also urged Cameron to back the project and called for "a gift from the nation to her majesty" to mark her 60 years on the throne.

The ship's designer, Colin Mudie, said he had included a helipad to land twin-engine helicopters used by the royal family. There will be two VIP suites with sufficient security to host royalty and the vessel will also be equipped for industrial and commercial exhibitions and conferences, and provide corporate entertainment facilities.

"We of course kept the royal family informed, particularly because of Prince Philip's links to sail training," said Rosemary Mudie, partner in the ship design practice.

"We always understood they approved of it but couldn't be seen to be saying it was a good idea for obvious reasons."

The ship's backers are understood to be keen for the vessel to be built in the UK and that goal would be jeopardised if the project received government money because tenders would have to be sought from across the European Union to meet public procurement rules.