Boris Johnson warned he would not hesitate to "put on the brakes" if Covid-19 cases show signs of increasing as lockdown measures are slightly eased.
In an effort to reassure a nervous public about adjusting to living with coronavirus, the Prime Minister insisted he would not do anything that would risk a second peak in infections.
In his address to the nation setting out a "road map" out of the lockdown, Mr Johnson said "if there are outbreaks, if there are problems, we will not hesitate to put on the brakes".
Monitoring will take place at local, regional and national level, with the possibility of targeted lockdowns being reimposed if there is a risk of the infection rate - the R value - rising beyond one and risking an exponential rise in cases.
With the death rate and number of hospital admissions currently in decline, Mr Johnson said: "It would be madness now to throw away that achievement by allowing a second spike."
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Under the test, track and trace programme - with the help of the new NHS Covid-19 app currently being trialled on the Isle of Wight - officials hope to identify and isolate any new outbreaks before the infection gets out of control.
The increased testing capacity - which Mr Johnson has promised will reach 200,000 by the end of May - should help public health officials identify new cases.
The app, provided it is downloaded by enough of the population, will help trace people who have been in close contact with a person who has developed coronavirus and advise them to self-isolate.
Alongside the software, ministers have also promised an army of 18,000 contact tracers to help identify and inform those who have been in contact with an infected person.
If clusters of cases are identified in an area, lockdown measures could be reinstated - although officials hope that a nationwide order will not be required.
Communities Secretary Robert Jenrick has previously said such measures could be quite specifically targeted.
"If, as we build up our infrastructure for testing and tracking and tracing, in time it is required for us to make interventions in smaller micro-communities where you are seeing the virus take hold again, then that will be something that we consider as other countries around the world have done when they have implemented effective track and trace systems," he said at a Downing Street briefing on Wednesday.
