An attempt to deploy a new submarine for Spain’s navy has run into problems again, after it emerged it cannot fit in its dock.

The S-80 boat was redesigned at great expense after an earlier mistake meant it had problems floating, and it was lengthened to correct the issue. Spanish newspaper El País now reports that after the changes, the docks at Cartagena can no longer fit the vessel. The cost for each has almost doubled, the newspaper said. It estimated that the cost of each S-80 “Plus” submarine would now be close to €1bn (£900m).

The original problem with the submarine dates back to 2013, when it was discovered that it was about 100 tons heavier than it needed to be. That caused a problem for its buoyancy – so it could submerge, but might not come back up again.

The original design from state-owned defence company Navantia was for a 71m, 2,200-ton displacement vessel. Now, the S-80 Plus is an 81m, 3,000-ton boat. As a result, the base at Cartagena will have to be dredged and reshaped to accommodate the now-floating longer vessel, the El País report said.