The government's ability to test people for the coronavirus has been "insufficient" throughout the pandemic, said a committee of lawmakers.
The Science and Technology Committee said the capacity had not been increased "early enough or boldly".
He said a lack of capacity had led the first decisions in mid-March to reduce follow-up of contacts and to largely restrict testing to hospitalized patients.
No. 10 said the tests have since been extended to "an unprecedented scale".
Committee chairman Greg Clark said ministers should "apply the lessons" of the "slow" increases in testing in other areas.
In a letter to Prime Minister Boris Johnson, the Conservative MP added that capacity "is the engine of strategy, rather than the strategy behind capacity".
The UK dramatically increased its testing capacity throughout the month of April, although it has already been criticized for its initial slowness.
A target of 100,000 daily tests was initially reached on May 1, but was then missed for eight consecutive days before being reached again on May 10.
On Monday, after 100,678 tests were provided in the past 24 hours, the ministers announced a further increase in eligibility, with all children five and older now able to get tested if they show symptoms.
Increasing testing capacity was also seen as crucial to enabling a mass program to track infected people using an NHS app, which ministers want to launch across the UK "in the next weeks".
In his letter, Mr. Clark made several recommendations to the ministers.
He accused Public Health England (PHE) of having initially chosen to "concentrate" the tests in a limited number of his own laboratories and to increase its capacities "gradually".
He said it led to the decision to initially abandon contact tracing as a strategy on March 12, and that residents of nursing homes could not be tested when the virus spread at its own pace. faster.
He added that the evidence gathered by his committee from experts in South Korea, Hong Kong and Germany had shown that the need for mass testing was "identifiable from the start".
PHE defends its role
In response, PHE said it was "not responsible" for the UK's screening strategy, "led by the Department of Health and Welfare".
Its chief executive, Duncan Selbie, added that "any test facility with adequate technology and containment" could carry out the test it approved after the lifting of security restrictions on March 3.
"PHE did not compel or seek to control a laboratory, public, university or commercial, to carry out tests," he added.
The committee also said that the transparency of scientific advice to ministers should be improved and asked that summaries of the advice be published "now and regularly".
Increase in "unprecedented" tests
He added that although some scientific articles reviewed by the Scientific Advisory Group for Emergencies (Sage) have been published, 92 of a current total of 120 have not yet been made public.
A Downing Street statement said that test rates had increased "on an unprecedented scale", from 2,000 a day in early March to over 100,000 in May.
"Now all people aged five and older who have symptoms and need a test can get one – and we will continue to build that capacity," he added.
"This is an unprecedented global pandemic and we have taken the right steps at the right time to fight it, guided at all times by the best scientific advice."