Test and Trace boss Dido Harding should be sacked and replaced with a senior military figure, a senior Tory backbencher has said.
Sir Bernard Jenkin, who chairs the powerful Commons Liaison Committee, criticised the "vacuum of leadership" at the top of the under-fire scheme and said Baroness Harding should be given a "well-earned break".
His call for a shake-up of the Test and Trace scheme comes after the number of people reached hit a record low last week.
Official figures show just 59.6% of the contacts of people who tested positive for the disease being successfully contacted and told to self-isolate.
"There is a spaghetti of command and control at the top, which is incapable of coherent analysis, assessment, planning and delivery," Sir Bernard wrote in the Sunday Telegraph.
"The immediate priority is to fill the vacuum of leadership in Test and Trace, which is destroying cooperation and compliance.”
He later told Sky News the “capability needs to move up several gears” and said there was a "lack of an overall strategy" in the scheme.
Shadow Health Minister Rosena Allin-Khan said Baroness Harding's position was "untenable" but stopped short of calling for her to resign.
She said the system has been "catastrophic" and tracing should be handed back to local communities.
"(Baroness Harding's) position is very difficult, it's untenable really, but fundamentally this comes down to the responsibility of the Government, they have failed people," she said.
"There are people going into this Christmas period not knowing if they're going to be able to hug their elderly parent in a care home for the last time or not.
"We need to be speaking up for them and for that we need to put it back into the hands of our local public health teams."
But Cabinet Minister Brandon Lewis expressed confidence in her leadership.
"What Dido has done is put together and drive forward a team that has come on so much in the last few months," he said.
"We have got a scheme that has gone from having no test and trace - obviously before the virus - to building up a scheme now that means we have tested over 28 million people - that's more than anywhere else in Europe - more than 1.1 million now who have been contacted through the scheme.
"We want to see it improve, we want to see it grow and get better and better. That's how we fight this virus.
"But actually I think Dido and the team have done a very good job to get to where we are."
It comes amid mounting concern in Westminster over levels of public compliance with orders to self isolate.
Mr Lewis confirmed that the Government was looking at cutting isolation periods down to seven days - rather than the current 14-day requirement.
"Teams are looking at what we can do around those isolation periods. This will be scientifically-led," he said.
"We are not ready to make a final decision or announcement on that yet but we want to make sure we are moving with science and allow people to live and work within this virus as best as we can while always making sure we protect people's health and the NHS."
