Gordon Brown's shock that his family medical records were hacked

Rebekah Brooks, then editor of The Sun, contacted the Browns, informing them that she had obtained medical details about their four-year-old son Fraser

The crisis engulfing Rupert Murdoch's global media empire dramatically worsened last night when it was claimed that private investigators working for The Sun and The Sunday Times targeted the former prime minister Gordon Brown.

In another extraordinary day in the phone-hacking scandal, News International's denials that illicit newsgathering techniques stretched beyond the News of the World came under strain in the face of well-sourced claims that two of its other best-selling titles were also involved in serious wrongdoing.

As Scotland Yard launched a fierce attack on News International for undermining its new inquiry into the alleged bribery of police officers by reporters, it was claimed that private investigators for Britain's largest newspaper group attempted to access Mr Brown's phone, medical records and bank account.

Illegal attempts were made by a "blagger" apparently working for The Sunday Times to access Mr Brown's account from the Abbey National bank in 2000. In a letter to The Sunday Times' editor John Witherow, Abbey National's senior lawyer wrote: "On the basis of facts and inquiries, I am drawn to the conclusion that someone from The Sunday Times or acting on its behalf has masqueraded as Mr Brown for the purpose of obtaining information from Abbey National by deception."

Separately a tape obtained by the BBC showed a "blagger" identified as Barry Beardall seeking, also in 2000, to trick Mr Brown's solicitors into handing over details of the amount he paid for a flat in Westminster owned by one of Robert Maxwell's companies. A story claiming that Mr Brown had underpaid for the flat by up to £30,000 was the subject of a story in the paper.

In another case, in October 2006, Rebekah Brooks, then editor of The Sun, contacted the Browns, informing them that she had obtained medical details about their four-year-old son Fraser. The Sun subsequently published a story stating that Fraser had cystic fibrosis.

Friends of the Browns said Ms Brooks' call caused them considerable distress, as they were seeking to come to terms with the diagnosis, which had not been confirmed. Police are thought to have evidence that the News of the World's private investigator Glenn Mulcaire had targeted Mr Brown and his wife, Sarah. In a statement, the Browns said: "We are shocked by the scale of law-breaking and intrusion into our private lives."

News International – whose chief executive is Ms Brooks – said it would investigate the allegations. The targeting of Mr Brown came as emails indicated that the NOTW had been bribing a Royal Protection Squad officer for personal details about the Queen and Duke of Edinburgh. Prince Charles and his wife, Camilla, are also understood to have been informed by the new Metropolitan Police inquiry into phone hacking, Operation Weeting, they too may have been targeted by Mulcaire.

Completing an awful day for Mr Murdoch, the Government reversed its strong support for the tycoon's £9bn bid for BSkyB, whose full ownership would have given total control of its fast-rising revenues and the ability to cross-sell his newspapers to its 10 million subscribers.

The Culture Secretary, Jeremy Hunt, executed his U-turn in the face of public revulsion sparked by claims that Mulcaire had deleted emails from the mobile phone of the missing schoolgirl Milly Dowler, giving her family false hope she was alive. After visiting Nick Clegg in Downing Street yesterday, Milly's parents, Robert and Sally Dowler, called for Ms Brooks to resign. Mark Lewis, the family's lawyer, said: "They don't see why she should stay in the job. They see this as something that went right to the top."

As the cosy relationship between Scotland Yard and News International collapsed, the police took the extraordinary step of accusing Mr Murdoch's company of undermining Operation Elveden, its new inquiry into alleged payments by the NOTW to corrupt officers. Scotland Yard said an agreement by NI not to make public details of internal emails outlining the claimed payments had been breached by the "continuous release" of information, which is known to only a handful of individuals. They said it threatened to hamper the operation, which last week arrested the NOTW's former editor Andy Coulson.

The Met believed the existence of the emails, which were handed to it by News International in June, would be kept secret until at least early next month, to allow inquiries to be conducted into the alleged corruption involving about five serving officers.

But the BBC journalist Robert Peston disclosed the alleged payments to Royal Protection officers yesterday, after apparently receiving information about emails from News International. The police were last week concerned about news of imminent arrests in The Times. The Met said it believed there was "a deliberate campaign to undermine the investigation into the alleged payments by corrupt journalists to corrupt police officers and divert attention from elsewhere".

The fallout appeared to have spread across the Atlantic, as shareholders filed a lawsuit stating it was "inconceivable" that James Murdoch and other board members were unaware of illicit newsgathering practices in his British newspaper group. The class action accused Rupert Murdoch of using News Corp like a "family candy jar".

Today, attention will shift to the Met's mishandling of the original investigation into phone hacking in 2007, and its subsequent insistence that there was no need to re-open the inquiry.