Protests by English Heritage (EH) and the Environment Agency have been swept aside by planners, who insist EPR Architects' proposal for a 4,446m 2four-storey block and café is 'innovative' and 'bold'.
The development, known as Bridge House, involves destroying historic stone steps and a basement terrace leading to Blackfriars Bridge.
Bridge House will also rise in the foreground of St Paul's Cathedral and obscure views of the Grade II-listed Unilever House.
In a statement, the City of London planning department said: 'The proposed building is of high-quality modern design and is of an unusual form. It presents an innovative response to the site characteristics and would make a bold statement.'
But Environment Agency planning liaison officer Tricia Lloyd disputes the planners' verdict and is calling for a buffer zone between Bridge House and the River Thames.
She said: 'There should be no erection of buildings any further than the edge of the underpass. The existing building on the site is set 18m from the River Thames, which currently allows for a valuable green space. The current proposals would lead to a loss of the existing buffer zone, which is unacceptable.'
EH agrees with the agency's objections by suggesting the design fails to show 'appropriate reference' to its wider context.
An EH spokeswoman said: 'The proposed building, which hangs over both roadway and riverside walkway and leans out toward the river, destroys the building line of the riverside and is not a sympathetic addition to the setting of adjacent and nearby listed buildings.'
EPR's scheme will now go before the City of London's planning and transportation committee on Tuesday, where it is expected to encounter renewed attacks from the Environment Agency and EH.