It is understood that an inferior quality steel was used, rather than the one specified, and that this has resulted in the canopy having to be dismantled.
An internal inquiry is under way into how the wrong type of steel was used and it is understood that a team of experts has been called in to make a report.
A source at Doncaster Metropolitan Borough Council said: "Every steel component has to be replaced. The problem resulted from steel made from wrong kind of alloy being used for the canopy."
The steel occurs in connection nodes that hold together a timber space frame. The 6 m high frame is used to support 1200 m² of photovoltaic panels.
A project insider said the type of alloy in the nodes made them too brittle, causing them to fracture and split. This has meant that they are unable to support the timber frame.
Carpenter Oak & Woodland Company, the subcontractor responsible for the timber frame's design and erection, confirmed that there was a problem with the steel but declined to comment further.
Steel supplier Avonmouth Fabrications was unavailable for comment.
The scheme was designed by Feilden Clegg Bradley. Partner Peter Clegg said: "Work has stopped on site while contractor Taylor Woodrow Construction sorts out the problem. As I understand it, the steelwork is eastern European."
A joint statement by the Earth Centre and design-and-build contractor Taylor Woodrow said: "Taylor Woodrow Construction's in-house material scientists are assisting the technical analysis now in progress. Completion [of the canopy] was due for Christmas 2000. Due to steel fabrication problems centring around the connection nodes for the timber space frame, this has been postponed until the end of February 2001."
Structural engineer Atelier One was not available for comment.
The canopy is part of the £15m second phase of the £42m millennium project. When finished, it will generate 80 000 kW of electricity, meeting 30% of the site's electricity needs.
The Earth Centre was the first of the Millennium Commission's 14 landmark projects. Since opening in April 1999 it has failed the attract the number of visitors anticipated by the centre's business plan.
