In its writ, Birse said it called in engineer Halcrow to review the plans and that within days Mott MacDonald had agreed it would be unsafe to carry on building using its design.
The writ said that after the wall collapsed, the site was closed until the following spring, and that Mott produced another design for the bund. The writ said: "Because of Mott MacDonald's dilatory approach, works on the shear key design did not start until July 2000 but by September work stopped, because of the extensive difficulties attached to the design."
The writ added that Birse decided to stop work on the designs to mitigate its losses and that the relationship between the two firms then deteriorated. It said that when Birse stopped using the design, no more of its advice was used.
Birse originally tendered £1.6m for the work, then lowered its price to £1,480,905, but it said its losses reached a total of £3,302,368. The work involved the design and build of a chalk bund and the area between the bund and the shoreline.
The writ added that Birse did not make any allowance for design risk in its tender and rejected other more expensive tender designs as a result of Mott MacDonald's advice.