AMs are calling on council chiefs and the Welsh Government to find a permanent home for the Medieval Newport Ship as research indicated for the first time it was a two-decker capable of transatlantic crossings.

They urged Newport council and the Welsh Government to pull together to turn the wreck of the 15th century merchant vessel likened to a maritime “treasure” into a major tourist attraction for the city.

They spoke out after experts concluded the 115ft long, three-mast ship from the time of Columbus had not one, but two main decks, plus additional levels called a sterncastle and a forecastle.

The maritime experts believe the ship built with timbers from the Basque region was 36ft high from the keel to the sterncastle and overall including the main mast up to 80ft.

The timbers of the ship excavated at the site of the Riverfront Theatre in 2002 are currently stored at a unit on Maesglas Industrial Estate.

However, the unit’s lease will run out this autumn and no permanent venue has been found to preserve it.

William Graham, Conservative AM for South Wales East, said: “We knew it was an immense treasure and this new discovery confirms how important this vessel is in maritime history.

“Newport should be fighting to retain this treasure and display it adequately.”

Lindsay Whittle, Plaid Cymru AM for South Wales East, added: “This is really exciting and fascinating news and once again highlights the importance of ensuring the permanent future of this ship.

“While public money is tight it is important that all public bodies – including Newport council and Welsh Government – pull together and work towards making this wonderful medieval ship a major attraction for tourists. This ship needs and deserves a permanent home in Newport.”

Maritime experts used the “orphan timbers” which were not attached to the main structure of the wreck to create a new model of the vessel.

Nigel Nayling, 53, a maritime archaeologist at the University of Wales Trinity Saint David, said: “It is another very significant step in the research of the vessel.

“Now we have an image which is archeologically credible and the most likely and accurate we are ever likely to get of the Newport Ship.”

Plans to open a museum for the ship at the Newport Centre were discussed last year but are now understood to have fallen through. The Argus was told by the chairman of the Friends of the Ship in February that one estimate for a museum would be around £30 million.

Conservative Newport Cllr Charles Ferris, 61, of the Friends of the Newport Ship, said : “What is needed in the medium term is a suitable place to store the timbers which is accessible to the public to maintain the ship’s profile and public interest in the project.

“This new study of the ship’s timbers reinforces the significance of the vessel, the only surviving ship from the time of Columbus, and quite capable of making a transatlantic crossing.”

A council spokeswoman said: “Newport City Council recognises the historical significance of the ship as well as its national and international importance.

“However, it still has to deal with austerity measures and is exploring a range of options for permanent display, including the possibility of a trust taking over this responsibility.

“In the meantime, the council is committed to completing the conservation of the ship timbers and has already entered into a contract with York Archaeology Trust to freeze-dry the timbers.

“The project is moving out of its current base in Maesglas later this year when the lease ends and the council is finalising options for suitable storage.”

• A Newport Ship open day takes place today [April 26] at Unit 22 on the Maesglas Estate off Greenwich Road between 11am and 4pm.