Baroness Dido Harding’s chances of becoming the next head of NHS England have sharply diminished following Matt Hancock’s resignation as UK health secretary for breaching Covid-19 rules, according to several senior government officials.

Amanda Pritchard, the health service’s chief operating officer, is seen as a frontrunner if Boris Johnson opts for an experienced continuity candidate. The prime minister and Sajid Javid, the new health secretary, have a veto on the successor to Sir Simon Stevens, who is due to step down on July 30.

Harding, regarded in Whitehall as a close ally of Hancock, has seen her reputation badly tarnished during her time heading NHS Test & Trace, damned by the independent National Audit Office as having failed to make “a measurable difference” to the spread of the pandemic last year.

Yet the former TalkTalk chief executive has made no secret of her appetite for the top job in the NHS. One former associate said: “This is not a passing fancy . . . She’s been talking about [the chief executive role] with her inner circle for at least three years.”

Following Hancock’s resignation on Saturday after breaching social distancing rules, senior government officials with knowledge of the process suggested that Harding’s chances of snagging the post were fading.

An ally of the prime minister said he “did not want further controversy” at the Department of Health and Social Care, adding: “I can’t see Dido getting the nod, especially after the last couple of days.”

Unlike Hancock, Javid is not a close friend of Harding, according to the new health secretary’s allies. “I’ve never thought of her as a frontrunner and that won’t change,” one senior Tory said.

One senior Conservative MP said: “There’s no chance [Harding’s] going to get it. It would be politically toxic, given how disastrous test and trace has been. Hancock was the only one pushing her.”

However, a senior Downing Street official insisted it was an “open process” and no formal decision had been taken on which candidate would be favoured to succeed Stevens.

Harding has close ties to the centrist wing of the Tory party. She is married to John Penrose, the MP for Weston-super-Mare. She is also a steward at the Jockey Club, whose Newmarket racecourse is situated in Hancock’s constituency. Both the former health secretary and Harding have ridden competitively as jockeys.

Referring to the 5m now waiting for hospital treatment, the highest number since records began in 2007, one former official added: “Dido’s perfectly capable of doing the job but the argument against her is that she brings too much heat into a situation which is going to get only more difficult.”

Whitehall insiders said Downing Street was still weighing whether it wanted a seasoned health service insider, able immediately to grasp the reins of a pandemic-battered NHS, or a “change agent” from outside the system who could think radically about how to ease the strain on the health service.

Javid has yet to indicate to officials his preferred choice to lead the NHS. As well as Pritchard, other candidates are understood to include Sir James Mackey, head of the NHS in Northumbria, Tom Riordan, chief executive of Leeds city council, and Mark Britnell, vice-chair of advisory service KPMG and a former long-serving senior NHS executive.

Riordan, Britnell and Northumbria Healthcare NHS Foundation Trust all declined to comment.

Pritchard never publicly confirmed her candidacy and could not be reached for comment. However, Stevens’ low-profile deputy attracts broad support among NHS board members, according to one person familiar with their thinking, although another insider stressed that no final view had been reached on the candidates.

One supporter said Pritchard’s deep well of frontline experience as chief executive of Guy’s and St Thomas’ NHS Foundation Trust, one of the country’s flagship hospital trusts, from which she was seconded two years ago to her current role, would leave her strongly positioned to lead the health service out of the crisis.

However, one person close to the process said that Downing Street had not ruled out hiring someone who has never worked in the health service, provided they were able to demonstrate a deep understanding of politics, and the relationship between the NHS and government. Riordan could fit that bill, the person suggested.

DHSC declined to comment. Harding also declined to comment.