Harri is also reported to have told the BBC that ‘good friends in No 10’ could also be deployed against them.
Harri announced last week that he was moving to become director of comms at News International, to be replaced by Walden at City Hall.
The news comes ahead of a day in which former PM Tony Blair will speak before the Leveson Inquiry into press ethics, which is now focusing on the relationship between press and politicians.
When contacted by The Guardian, Harri said: ‘It was my job at City Hall to ensure fair coverage for the mayoralty and I did what I could over four years to deliver that in a professional and courteous manner.’
He insisted that his comments about No 10 were not a threat but merely reflected the broader frustrations he claims were felt not only inside City Hall but in ‘central government, the Olympics family and some within BBC London itself’ about the relentlessly hostile coverage.