Charities that continue to contact potential donors without offering an opt-out could be fined as much as £25,000 by the Information Commissioner’s Office
Charities with "extremely aggressive" fundraising practices could be fined up to £25,000 if they do not crack down on nuisance calls, emails and letters.
Organisations must comply with new data protection legislation and provide marketing opt-outs from Thursday.
It comes after a 92-year-old poppy seller killed herself after being overwhelmed by requests from charities.
Fundraising Regulator chairman Lord Grade said "such terrible practices" could not be tolerated.
‘Not an isolated case’
Lord Grade, a former BBC and ITV executive, said that stories of aggressive fundraising and its consequences shocked Britain after the suicide of poppy seller Olivia Cooke.
In 2015 Mrs Cooke took her own life after receiving 466 mailings from 99 charities in a single year.
Her friend said she had been put "under pressure" by persistent charity fundraisers, but added the "pestering" was not entirely to blame for her death.
The Bristol resident, who had 27 standing orders to different charities at one stage, suffered from depression.
The Fundraising Standards Board found that 70% of the charities who contacted Mrs Cooke had acquired her details from third parties.
Olive Cooke had been selling poppies for the Royal British Legions for 76 years, before she committed suicide in May 2015
Speaking on the Today programme, Lord Grade said: "Sadly this wasn’t an isolated case, and as a result of that high-profile tragedy it was clear that there was bad practice across many charities."
Charities now have to comply with new data protection legislation, preventing fundraising companies from sharing personal data or potential donation targets.
Fundraisers must also clearly provide an opt-out for marketing on all communications (texts, letters and phone calls) to potential contributors.
The Fundraising Preference Service (FPS) was set up after a cross-party review into the self-regulation of charity fundraising. The review was called by David Cameron after Mrs Cooke’s case.
Announcing the new body, he said: "You go online through our website or through a charity’s website and you can send a message that you do not want to hear from any charities, or you only want to hear from charities you select."
He added that people with no access to a computer can call up by phone.
If charities do not adhere to new regulations, they will be referred to the Information Commissioner’s Office and prosecuted under the Data Protection Act 1998.
Lord Grade added: "Many [charities] have embraced the new world, but charities have to understand that the fabulous generosity in the wallets of the British public cannot be taken for granted."