The Wembley arch is 315 metres long

Project bosses said their safety checks showed more work is required on the complex 2,000-tonne structure.

Computer tests have shown weak spots due to welding faults and there are problems with the concrete foundations.

Engineers say "some minor rectification work" is being carried out, but the 315 metre-long piece will be raised onto the new �757m stadium in the spring.

Ashley Muldoon, project director for Multiplex Construction UK, the main contractor for the Wembley Stadium project, said: "There are no structural problems with the construction of Wembley Stadium.

"Extensive quality assurance checks are carried out on-site on a regular basis. These are procedural and on occasion, some rectification work is required.

"The project is running ahead of schedule and Multiplex is confident that we will deliver it on time and to budget."

The firm also said the defects were discovered during "quality assurance checks".

The stadium remains on target to open in 2006 with the 2006 FA Cup Final set to be the first match played there.