Work on one of the two ferries being built on the Clyde was subject to further delay and cost over-runs because of the need to replace the wrong type of steel and pipework.

David Tydeman, the chief executive of Ferguson Marine, told MSPs there were a number of “mistakes” during the building of MV Glen Sannox.

A mild steel had been used on the clamshell doors rather than stainless steel while galvanised pipe was used in areas it should not have been used.

Mr Tydeman told MSPs on the net zero, energy and transport committee that these errors had contributed to the delays and rising costs.

He said that almost 10% of the final price tag — about £35 million — had been spent on redesigning the Glen Sannox, adding that not having a fixed design had been at the root of many of the problems.

Some work had to be done “twice or even three times” because of the re-routing of pipework and cables.

He said: “One example would be the hydraulic pipework associated with opening the clamshell doors. That was all installed by mild steel and should have been stainless steel. We had to take all of that out and redo it.”

The steel had been “wrongly specified” by the design team. “It has to be in stainless steel, a simple error which was missed,” he said.

“We have had galvanised pipe used in areas it shouldn’t have been used and had to change that as well. We have had lots of mistakes.”

These mistakes added to earlier errors over the size of doorways and the number staircases which had led to safety concerns. Additional stairs have been installed while 17 further doors have been ordered to meet the stipulations of the Maritime and Coastguard Agency.

The MV Glen Sannox is expected to go for sea trials in the early part of next year and the second ferry, the MV Glen Rosa, likely to follow towards the end of 2024.