Charities could face criminal sanctions for bullying the public into giving money, their regulator has warned.
Fines could be brought in as part of the first statutory regime for fund raising, after concerns were raised about the way some charities collected their money, following the suicide of Britain's longest-serving Poppy seller Olive Cooke.
Mrs Cooke, 92, from Fishponds in Bristol, told how she was receiving up to 267 letters in a month and regular phone calls from charities asking her for donations.
Her family later said that while the calls and letters were intrusive, they were not to blame for her death. An inquest into her death did not hear any evidence concerning charities.
Charity Commission chairman William Shawcross told The TImes that if charities failed to address abuses, his organisation was willing to regulate street "chuggers", door-to-door collectors, call centres and direct mail appeals.
He also accused the RSPCA of grotesque conduct, saying that it was inadequately run, and claimed that charity money was being diverted to Islamist terrorist-related causes.
In the wake of Mrs Cooke's death, the Government commissioned a review by Sir Stuart Etherington, chief executive of the National Council for Voluntary organisations.
Mr Shawcross said: "If he concludes that self-regulation by charities cannot work, then government would have to consider whether the Charity Commission should regulate fund raising."
Under the new regulations, charities and the fund raisers they employ would be banned from high-pressure tactics, repeatedly targeting people and making misleading claims.
Mr Shawcross said the RSPCA was "a wonderful organisation that has a great deal of affection", but said it "hasn't been run and governed as well as it should have been in the last few years".
He criticised the charity's "zeal for prosecutions", citing the case of a pet cat that was removed from its home and put down without the family being able to say goodbye, and said the RSPCA's opposition to the badger cull "overstepped the mark politically". And he expressed concern over the appointment of "radical" trustees, including one who said farming was like the Holocaust.
RSPCA spokesman David Bowles said he was "surprised" by Mr Shawcross's comments, as they were "completely contrary to what his staff and what his chief executive said".
Mr Bowles told the BBC Radio 4 Today programme: "We have been working very closely with the Charity Commission, particularly over the past few years. We had them in only a month ago and they said they were very satisfied with what we were doing, they recognised that our tone of voice had changed, they were very happy with us, they thought we were responsible and we were acting in a very good way."
He added: "The word `zeal' is very inadvisable to use for him. Obviously, the RSCPA ... does take over 80% of prosecutions, so essentially we do the Government's job and save the Government £50 million or so each year because we do that job. I'm very pleased to say that in the past two years prosecutions have come down by about 30%."