The Information Commissioner’s Office will investigate potential data and privacy breaches at four large charities and the fundraising agency GoGen after allegations were made in today’s Daily Mail newspaper that the agency was "exploiting loopholes" in the Telephone Preference Service.

The newspaper’s front page today carried the headline "Shamed: Charity cold call sharks", with a further four pages devoted to the findings of a Mail journalist who spent a fortnight undercover at GoGen’s London call centre. The paper names the four charities accused of TPS breaches as the British Red Cross, Macmillan Cancer Support, the NSPCC and Oxfam.

Oxfam, Age International and Cancer Research UK all said that they had suspended their work with GoGen after the story was published.

The paper accuses GoGen, which works for some of the country’s biggest charities, of being "aggressive, ruthless and cynical", with supervisors telling staff to make "more ferocious asks" and that nobody had an excuse not to donate.

It claims that people were asked to donate even after revealing they had dementia and that fundraisers told donors that half of their donation would go GoGen itself only after they had handed over their bank details.

It also says fundraisers working for the British Red Cross, Macmillan Cancer Support, the NSPCC and Oxfam called people who had asked not to receive unsolicited calls having registered with the TPS.

The paper says that the agency was exploiting a loophole in the TPS regulations enabling people to be called if they had given their consent in other ways to receiving calls, such as in the small print when making a donation.

A spokesman for the ICO said it was looking into GoGen and those four charities, saying: "We will be investigating whether there have been any breaches of the Data Protection Act or the Privacy and Electronic Communications Regulations."

The spokesman said that the maximum penalty for such breaches was £500,000, although the ICO had never issued a fine of that amount.

However, he said that in April the rules concerning nuisance calls and texts were strengthened – before that, the ICO had to prove that such calls "caused substantial damage or substantial distress", something it had previously failed to do in court. Under the new law, the ICO simply has to show that a serious breach of the law took place.

A statement from Giuseppe Iantosca and Bob Metrebian, directors of GoGen, said they "refute many of the allegations made in the article and will be taking legal advice regarding our position". They said they were considering making a complaint to the press regulator IPSO. The statement said: "At no time do we make calls to any TPS-registered supporter without the full support and permission of the charity in question."

Their statement said the company had consented to the Fundraising Standards Board conducting a "thorough investigation" of the allegations concerning vulnerable adults. It said the agency’s training "emphasises the sensitivity of speaking to vulnerable individuals". It pointed out that staff filmed making what it admitted were "totally unacceptable" statements quoted in the piece were all "very junior" and "still on probation", and four of these people had been "suspended pending further investigation". The statement said the company was reviewing its criteria for promotion to trainer and supervisor roles.

Alistair McLean, chief executive of the FRSB, confirmed that an investigation "to establish whether any breach of fundraising standards has taken place" had begun and said the allegations were "of grave concern to us".

The four charities implicated in the ICO investigation all issued statements underlining the importance of fundraising income to the work and promising to look into the allegations.

In a statement posted on Oxfam’s website, Tim Hunter, its director of fundraising, said: "Following these allegations we temporarily suspended all telephone fundraising activity to ensure companies who work on our behalf meet not only the regulatory standards but also our own high moral and ethical standards."

A spokeswoman for the BRC said: "The behaviour of the trainers and supervisors filmed by the Daily Mail is absolutely unacceptable and we are deeply disappointed." She said the charity was calling on the ICO and the Institute of Fundraising to "urgently review" their official guidance on contacting people registered with the TPS.

A spokeswoman for Macmillan said the charity "takes the claims made by the Daily Mail extremely seriously and are looking into these as a priority". A spokesman for the NSPCC said: "Any suggestion of inappropriate activity is deeply worrying and we would always want any concerns to be raised with us immediately so that they can be quickly addressed."

Alongside those four charities, the article also names Age International, Cancer Research UK and Save the Children as GoGen clients. Nick Georgiadis, head of direct giving at CRUK, said: "We take these allegations against GoGen very seriously and we have suspended all activity while we investigate this matter urgently."

Chris Roles, director of Age International, said that GoGen had been "working on a small project" for the charity since May, which had now ended. "We have limited other activity with GoGen which is currently on hold," said Roles.

Rob Wilson, the Minister for Civil Society, said: "The evidence is mounting that totally unacceptable practices are taking place by fundraisers. These allegations need to be investigated thoroughly by the regulators, and charities should be ensuring that these immoral practices are stamped out for good."