The heritage watchdog has written to the City's head planning officer Peter Rees demanding that the planned 63-storey tower - which would be the tallest building in Britain - be rejected.
This opposition will set up the latest planning battle in the capital, which will be exacerbated by the fact that the scheme is being heavily backed by CABE.
In the letter, EH's head of London regional advice Paddy Pugh claimed the skyscraper, proposed for a site on Bishopsgate, would damage historic views from St James' Park, the Tower of London and Tower Bridge.
In addition, Pugh's letter says KPF's vast scheme would 'cause material harm' to a series of listed buildings within the City, including the Royal Exchange building.
'Significantly,' the letter says, 'We are not convinced that this harm [to the setting of the historic buildings] would be balanced by an enhancement of the surrounding public realm or any other community benefit.
'These proposals are of greater than local significance,' the letter adds. 'If built they would have a major impact upon London's historic environment beyond the boundaries of the City'.
And Pugh's letter goes on to warn that if the Corporation's planning committee grants KPF permission, EH will write to John Prescott to demand that it is called in.