The total cost of building the new Wembley stadium has risen almost 40% to £660m. The estimated price in June was £475m.

Developer Wembley National Stadium Limited is seeking £410m in loans. The developer's loan arranger, Chase Manhattan bank, is contacting investors this week in a bid to raise extra funds.

Demolition work on the existing stadium cannot take place until all funding is in place.

A WNSL spokesman said the overall cost of the project was estimated to be "£600m-ish", with an additional £60m needed to cover interest on the loans.

The figure includes the £326.5m construction contract, section 106 agreements, the purchase of the site, the return of £20m of lottery money and contingency funds, the spokesman said.

The additional funds will be provided against an assurance by WNSL that it will be able to raise sufficient funds in the future to pay back the loans.

"We have a guaranteed maximum price. Our business plan is set against the performance of our business income, such as income from television rights," said the spokesman.

WNSL does not anticipate that the scheme will run overbudget. "We have spent a long time getting to this starting point. Detailed plans are in place," the spokesman said.

Australian contractor Multiplex won the construction contract in September. The original construction cost was put at £340m.