The development is the latest high-profile London win for McAlpine. The contractor was selected to work on Arsenal FC's new stadium in January.
A source at the client, the Spitalfields Development Group, said McAlpine would be working up a new price for the scheme. This is because of changes that have been made to the scheme since a revised design for the sensitive City of London site was unveiled by architect Foster and Partners last December.
The source said McAlpine would be confirmed as the project's contractor in April. The source commented: "There is a lot to be done – we have got to get the right price first. It will probably be mid-April when we press the final button."
A revised planning application for the scheme is due to be lodged in the next few weeks. In the latest design, the shape of the development's main block, which varies in height from six to 12 storeys, will be switched from a slope to a stepped effect.
A development source said: "It's no longer sloping; it's not a change to the design, but a tweak."
There’s a lot to be done – we have got to get the right price first
Source at the Spitalfields Development Group
The move is thought to follow concern about the scheme from architectural watchdog CABE. Foster and Partners was forced to change the scheme from two buildings to one last year after residents and market traders expressed their unhappiness.
English Heritage is also understood to have raised objections to the scheme.
Proposals for the project, which is near Liverpool Street Station, were first put forward by developer SDG 14 years ago.
The first is a construction management deal to build a £22m office in Granton, Edinburgh, for developer Lattice Properties. The scheme will be on site in March and is due to be completed in late 2003.
The second scheme is a fixed-price £22m contract to build the Bexley Business Academy, a new business school in south-east London that will replace the Thamesmead Community College. ISG will use its construction arms Interior and Exterior on both projects.