A senior project source said the £10m figure was "not a million miles away" from the total claims that package contractors have submitted to the client so far.
An industry source said there may be a contingency allowance of about £5m in the opera house's £140m construction budget, but added that he did not know where the £5m balance could come from. This means that the project is in danger of running out of money.
The principal claimant is Balfour Kilpatrick, which is carrying out the M&E work. The late running of this has impacted on the other internal trades, which are asking for £5-6m in compensation.
The claims have been submitted to the project's construction manager, Schal. However, Schal director Paul Reeder, who was recently transferred to work on the opera house, was sanguine. He said: "Here, generally, we are within the overall budget at the present time. We don't envisage that we will exceed the budget.
"Yes, there are claims, but we believe we have managed to cater for these eventualities by the way we let the packages.
"In terms of the overall cost, the claims are not significant, but it's really a matter between the opera house and its trade contractors." Acknowledging that there is little leeway for asking a lottery project client for extra cash, Reeder said: "If you are dealing with an office block in the City, the client might throw money at the project to get it done. Here, you can't pick the client's pocket, so to speak," he said.
Reeder said Schal is attempting to finalise agreement of accounts while firms such as Balfour Kilpatrick are forging ahead with their work.
The redevelopment is due to be ready by September, which would allow rehearsals to start in time for a 1 December 1999 opening.
Reeder said he could not see any reason why the team should miss the September deadline, and that off-site testing of £15m worth of stage equipment is taking place.
However, industry sources are sceptical of Schal's chances of making its September target. "One thing is for sure," said one, "that equipment won't work the first time it's tested." One project source said Schal is bracing itself to continue work after the opening night by completing the auditorium before the opera house offices and retail space.
On site, there is still discontent among electricians who have complained about the transfer of three colleagues – one a former steward – to a site in Wales.
They were due to meet employers this week or next week to discuss the dispute, which could lead to a walkout on the project if it is not settled.
Meanwhile, there are also signs that steel erectors working on the opera house's delayed fly-tower have joined Millennium Dome erectors in protesting about their national pay deal.
Workers are also unhappy about some bonus payment schemes on the dome.
