Jeremy Hunt was braced for fresh revelations on Friday as his former special adviser and top civil servant gave more evidence to the Leveson Inquiry into media standards.
Labour has renewed calls for Hunt to quit after the inquiry was shown a memo he sent to Prime Minister David Cameron arguing the case for News Corporation to take over BSkyB, just weeks before he was given quasi-judicial oversight of the bid.
The note warned that Business Secretary Vince Cable's decision to refer the bid to regulator Ofcom could leave the Government "on the wrong side of media policy".
More emails and text messages are expected to be published as the Culture Secretary's ex-special adviser, Adam Smith - who resigned after admitting getting too close to News Corp lobbyist Fred Michel - returned to give further evidence to the inquiry.
With pressure mounting on Hunt, William Hill has shortened the odds on him being the next cabinet minister to leave to 1/2 favourite.
“Mr Hunt's pursuers are scenting a high profile victim but Mr Cameron will be determined to foil them, at least in the short term”, said Graham Sharpe, a spokesman for the bookmaker.
Hunt was photographed on Friday going for a jog in central London.
Also appearing before Lord Justice Leveson will be the senior civil servant at Hunt's Department of Culture Media and Sport, Permanent Secretary Jonathan Stephens.
Stephens was dragged into the row after Hunt told MPs he had "approved" the nomination of Smith as a point of contact with News Corp. The civil servant repeatedly refused to confirm or deny this during a subsequent appearance before a parliamentary committee, and later said in a letter only that he was "aware and content" with the arrangement.
In his memo to the Prime Minister, sent in November 2010, Hunt warned that News Corp's James Murdoch was "pretty furious" over the Ofcom referral for the company's offer to buy the 61% share of the satellite broadcaster which it did not already own.
The culture secretary told Cameron that News Corp's plan to create a multi-platform operation gave the UK "the chance to lead the way" on media globally. Without it, Britain's media sector would "suffer for years", and it would be "totally wrong to cave in" to opponents of the move.
Labour said the memo contradicted an assurance Hunt gave the House of Commons in April this year that he made "absolutely no interventions seeking to influence" the decision on the BSkyB while Mr Cable was overseeing it.
Shortly after the memo was sent, Cable was stripped of his quasi-judicial role after being secretly recorded saying that he had "declared war" on News Corp boss Rupert Murdoch, and the responsibility was handed to Hunt.
Labour deputy leader Harriet Harman said: "It is clear... that David Cameron gave responsibility to Jeremy Hunt for deciding on the BSkyB bid when he knew only too well that the Culture Secretary was actively supporting the bid.
"The Prime Minister should never have given him the job.
"It is clear that Jeremy Hunt was not the impartial arbiter he was required to be, and he should already have resigned."
But Downing Street played down the memo's significance, pointing out that Mr Hunt had already made supportive comments about the bid in press interviews earlier that year.
A Number 10 spokesman said: "Jeremy Hunt's note is entirely consistent with his public statements on the BSkyB bid prior to taking on the quasi-judicial role.
"It also makes clear that 'it would be totally wrong for the Government to get involved in a competition issue which has to be decided at arm's length'.
"The PM has made clear throughout that he recused himself from decisions relating to BSkyB and did not seek to influence the process in any way."
A source close to Hunt also said there was nothing in the memo that suggested he should not have been given the quasi-judicial function.
"Jeremy is clear in the memo, as he was throughout the bid process, that it should only go ahead if it addressed the plurality concerns," said the source.
On Thursday, Smith told Leveson that he had perceived his role as "managing relationships with interested parties" and "one of the points of contact for News Corp", but said he had received no "direct instruction" from Hunt on how he should do this.
Earlier, the inquiry heard that Michel exchanged more than 1,000 phone calls, emails and texts with Hunt and his team during the takeover bid, which was abandoned in July 2011 amid the furore over phone-hacking at News Corp's News of the World newspaper.
The lobbyist suggested that the Culture Secretary knew Smith was feeding him details of the government's thinking about the proposals.
But he insisted he never had "inappropriate" contact with Hunt or his officials while campaigning for the BSkyB takeover to be approved.
Harman told BBC Breakfast the evidence of Hunt's wrongdoing was "absolutely massive".
Instead of judging the Murdochs' bid, he was backing it, she argued.
"There are two bits of evidence, actual straightforward evidence, that Jeremy Hunt was not impartial, he was meddling before he even took over the bid and was on the side of the Murdochs," she said.
"The first was that he had to be warned off by the civil servants not to have any more meetings with Rupert Murdoch but he kept up the contact through his special adviser, and secondly he wrote a memo to the Prime Minister."
Former Prime Minister Tony Blair is scheduled to appear before Leveson on Monday.
Here's a gallery of politicians enjoying a jog in times of crisis: