DPP Alison Saunders announced her decision after News of the World reporter Lucy Panton successfully appealed against her conviction after juries in the cases that had already gone to trial failed to convict those accused.
However, cases against three journalists and numerous public officials were still due to go ahead at the time of going to press.
Former Daily Mirror journalist Greig Box Turnbull, who had his case dropped, described the process as "a vicious assault on public-interest journalism and press freedom by the Met police and the CPS".
The backlash has now begun with calls for a public inquiry into the £20m cost of Elveden – which has so far failed to secure a successful conviction – with some describing it as a waste of public money due to its failure to take account of the "public’s right to know".
The Sun’s Tom Wells, who was cleared by a jury last month, said his trial demonstrated that his stories had "shone a bright light into areas of public life which those in authority would have far preferred to have kept shrouded in darkness".
In his closing remarks to court, the journalist’s lawyer, Adrian Keeling QC, quoted the words of the newspaper baron Lord Northcliffe: "News is what someone, somewhere, wants to suppress. All the rest is advertising."