ITV News Correspondent Rebecca Barry reports
Meanwhile, as few as one in four people testing positive for Covid-19 receive their results in 24 hours.
The Test and Trace system reached just 68.6% of close contacts of people who tested positive for Covid-19 in England in the week ending September 30, the lowest since the scheme began.
The figures are starkly different to those cases handled by local health protection teams where 97.1% of contacts were reached and asked to self-isolate in the week to September 30.
For cases handled either online or by call centres, 62.4% of close contacts were reached and asked to self-isolate.
Further statistics reveal just 25.7% of people who were tested for Covid-19 at mobile units in the same week received their result within 24 hours, down from 38% in the previous week.
Only 2.4% of people in England who used a home test kit for Covid-19 received their result within 24 hours.
Prime Minister Boris Johnson had pledged that, by the end of June, the results of all in-person tests would be back within 24 hours.
He told the House of Commons on June 3 that he would get “all tests turned around within 24 hours by the end of June, except for difficulties with postal tests or insuperable problems like that”.
On Tuesday, it was revealed that almost 6,000 of nearly 16,000 people in England who tested positive for Covid-19 but whose cases were not recorded for up to a week due to a technical error have not been reached for contact tracing purposes.
The shadow health secretary said on Monday up to 48,000 people were not alerted to the fact they had come in to contact with someone who had tested positive.
Of the 34,494 people transferred to the Test and Trace system in the week to September 30, 74% were reached and asked to provide details of recent close contacts.
This is the lowest percentage since the first week of Test and Trace (the week to June 3), when the proportion reached was 73.4%.
A total of 51,475 new people tested positive for Covid-19 in England in the week to September 30, according to the latest Test and Trace figures.
This is an increase of 56% in positive cases on the previous week and is the highest weekly number since Test and Trace was launched at the end of May.