Last week the Enquirer revealed that Balfour was haggling for up to £50m to meet soaring costs on its job to fit the world’s largest single span cantilever roof .
Balfour is believed to be on schedule, but technical problems with the roof structure required steel contractor William Hare to carry out extra strengthening work.
This has driven the original project cost up by nearly a quarter to close to £190m.
A statement from stadium operator, the LLDC, said: “This is a unique two year transformation project and a hugely complex engineering scheme, using techniques previously employed on oil rigs.
“Providing adequate support for the new roof has required significantly more strengthening work to the main roof truss, which was originally designed to be taken down after the Games.
“We have therefore today agreed to increase the value of the Balfour Beatty contract by £35.9m to £189.9m.
The LDDC stressed the bill would not be footed by the tax payer with the cash being drawn down from contingencies and income from other developments.
“We will meet these costs from the project contingencies and additional income we will generate from our other developments.
“There will therefore be no additional call on the taxpayer and no impact on our current programme.”
Balfour was awarded the contract in January and is running against a fixed deadline to complete the first phase of the conversion to host games for the 2015 Rugby World Cup.
After the tournament Balfour will return to finish the conversion and create a permanent home of West Ham from 2016.