The decision backed by all four CMOs comes after the Joint Biosecurity Centre recommended a shift from Level 4 alert status - in which coronavirus is considered to be in general circulation with transmission high or rising exponentially - to Level 3, meaning simply that the virus is in general circulation.
A statement from the four CMOs says: 'There has been a steady decrease in cases we have seen in all four nations, and this continues.
'It does not mean that the pandemic is over. The virus is still in general circulation and localised outbreaks are likely to occur.
'We have made progress against the virus thanks to the efforts of the public and we need the public to continue to follow the guidelines carefully to ensure this progress continues.'
Figures from the Office for National Statistics (ONS) show deaths in England and Wales are now close to the five-year average, after a peak in April during which deaths in successive weeks were more than double the five-year average.
COVID-19 was mentioned on close to 9,000 death certificates in a single week at the height of the pandemic, the ONS data show.
The decision to reduce the UK's COVID-19 alert level comes after GP leaders demanded clarity over plans to ease restrictions for the 2.2m patients on shielding lists.
The RCGP warned this week that practices would struggle to answer thousands of questions from anxious patients amid reports that shielding could be dropped from the end of July.
The government in Northern Ireland this week confirmed that it would end shielding from 31 July. The UK government has yet to clarify its plans but has promised an update soon.
Northern Ireland health minister Robin Swann said this week: 'We have now reached the point where, if the current trends continue, there will be no need for anyone to shield after 31 July.
'Letters we issue will provide details of the support which will continue to be available up to and after 31 July. While my announcement today will be welcome news for many who are shielding, some will view the prospect of an end to shielding with great anxiety. I want to assure them that they should decide what to do at their own pace. Everyone will approach this situation differently.'
A DHSC spokesperson said: 'We are considering the next steps for the shielding programme beyond the end of June, based on the latest medical and scientific advice.
'No final decision has yet been made and we will set out more detail shortly.'