A company involved in the new Wembley Stadium has issued legal proceedings against the project's main contractor.
The stadium arch is more than 400ft tall
Cleveland Bridge has announced it has stopped all work on the contract and is to take action against the stadium's project leader Multiplex.
It says the proceedings are for alleged breach of contract and claims Multiplex owes it money.
The company warned the decision to stop work on the project may mean redundancies at its Darlington plant.
Cleveland Bridge supplied a huge steel arch costing £60m, which is the centrepiece of the new ground.
In a statement, the company said: "Cleveland Bridge has advised Multiplex that it has no alternative but to cease all work on the Wembley Stadium contract... and has instructed its solicitors to issue proceedings against Multiplex in the Court of Technology and Construction in London."
It added: "Cleveland Bridge warned that the decision to cease work on the Wembley Stadium contract will cause a shortfall and may result in redundancies at its plant in Darlington."
A spokeswoman for Multiplex said the firm had no comment while it was taking legal advice.
Jimmy Skivington, from the GMB union, said: "It is very, very disappointing that we have found ourselves in this position, but it is something that we will have to deal with."
He said the union would be meeting with the company later this week and hoped the matter will be resolved with jobs being kept in Darlington and the company finishing the contract.