The head of NHS Test and Trace has defended paying consultants on average £1,000 per day, as she told MPs the service was having a “material impact” in the fight against Covid-19.

Baroness Dido Harding told the Commons Public Accounts Committee she felt it was “appropriate”  to bring in external help in “extreme emergency circumstances” such as that faced by the country during the coronavirus crisis.

Whitehall mandarins said they did not believe profiteering had gone on, despite the large daily rates forked out to the private sector, telling MPs that consultants had lowered their usual fees in order to assist with the pandemic.

Asked by MPs whether it was right for at least 900 workers to be earning on average £1,000 per day, Tory peer Baroness Harding said: “I think it is appropriate to build a service in extreme emergency circumstances using short-term contingent labour and consultants for some of those roles.

“I think they’ve done very important work alongside the public servants, the military, the healthcare professionals and members of the private sector who have come and joined us as well.

“We couldn’t have built the service without all of that combined expertise.”

The details regarding the number of consultants working in the service, which has a £22 billion budget and was formally started last spring, came during answers to the committee from David Williams, the second permanent secretary at the Department of Health and Social Care.

He said there were about 900 consultants from the firm Deloitte working for Test and Trace – down by approximately 100 since October – and said there was “a plan in place to see that number reduce markedly over the course of the next few months”.

MPs said that, as recently as November, there were 2,300 consultants and contractors working on the scheme.

Mr Williams added: “The average cost across our consultancy support – I imagine it is about the same for Deloitte – is around £1,000 per day.”

He said he did not want to “get into the specific detail of individual contracts” when asked about reports that some consultants were earning as much as £7,000 per day.

He promised to later write to the committee about the highest day rates paid by Test and Trace.

Pressed on whether he was confident that there had been no private sector profiteering from the Test and Trace budget, Mr Williams replied: “Yes, as confident as I can be based on the information that I’ve seen and based on the regular reporting that comes up through the Test and Trace commercial and finance staff.”

Baroness Harding told MPs on Monday that close to 1,000 people per minute were tested on Sunday, January 17, and that more than 7.5 million people had been successfully contact-traced since the start of the new year.

Asked about the Scientific Advisory Group for Emergencies (Sage) suggesting in September that the testing programme was having a “marginal” impact on transmission, she replied: “There is no doubt that as we have built and scaled the service, we have learnt more and more and we are now hitting all of the operational contact tracing targets that Sage set us.

“We are reaching more than 80% of people who test positive, we are reaching more than 90% of their contacts and the 92% of all contacts we reached last week – three-quarters of a million people – 97% of them we reached in less than 24 hours.

“So, no, I don’t believe we are having a marginal impact, actually. As measured, we are having a material impact in the fight against Covid.”