Squire and Partners recently reduced the project by five storeys in a bid to appease EH, but the conservation body does not believe the practice has done enough and has called for the project to be scrapped.
EH says there are three conservation areas within the City that would be detrimentally affected if the tower were to be given the green light in its current state.
A statement from EH said: 'The amendments that have been made recently involve only a modest reduction in height of the tallest tower and do not address any of our previous concerns.
'For this reason, we have again urged Islington to reject the scheme.'
The statement added: 'The main tower block would still loom over Finsbury Square, Bunhill Fields and Moorfields conservation areas and have a seriously detrimental impact on nearby listed buildings including St Luke's Church, Old Street, the honourable Artillery Company and the Leysian Mission.'