Professor Devi Sridhar, chair of public health at Edinburgh University, told Times Radio that, although lockdowns are "crude" and "catastrophic" for the economy and mental health, one is needed given the prevalence of Covid-19 across the UK currently.
But Prof Sridhar said a post-lockdown strategy must be put in place to suppress the virus going into the summer.
She said: "With the numbers we're at, there's no other choice.
"For me, it's a three-phase strategy – first is right now, it's crude, it's catastrophic for the economy and for people's mental health, but a lockdown.
"Get those numbers down, protect the NHS for the next 12 weeks."
She added: "When we get into March and hopefully numbers are low again and we get into seasonal change, get your testing and tracing and your border measures in place to really suppress.
"And then in the summer, instead of taking your foot off the gas and saying 'let's open up everything', actually think 'how do we prevent this winter from happening again? How do we actually protect that low prevalence, get emergency teams in place in case there are flare-ups ... go in, have a quick, sharp one-week lockdown and get your testing and tracing to clear the virus."
Prof Sridhar said the UK would be forced back into lockdown if there was not a greater plan to combat Covid-19.
She said the four nations would see cases rise again in the summer months if test and trace systems, mass testing and support packages for people self-isolating were not put in place.
Prof Sridhar said: "We are not at the mercy of this virus where whatever it does we have to react.
"We can dictate how this evolves but we need a bit more agency in being more proactive and ahead of it instead of always behind it."
The newly approved Oxford/AstraZeneca vaccine will be available in more than 1,000 locations in Scotland from Monday.
On the subject of vaccines, Prof Sridhar said questions still need to be answered about how much protection they would afford the public.
She described the three approved inoculations as a "bright spot", but said it was not yet clear how long immunity lasts for, if the vaccines stop people from being infectious or how much of the population would need to be covered to provide herd immunity.
"If you really want to get to some sort of true herd immunity, you're looking at 80-90 per cent of the population, which even with our current roll-out would take you into next fall,” she said.
"We need to make sure at that point, the people who have been vaccinated now still have immunity."
Prof Sridhar added: "For me, the vaccine is definitely there, we have to continue roll-out, keep saving lives through protecting vulnerable people with that.
"But it's not a strategy in and of itself and relying on it alone is highly, highly risky, especially with all the new variants and mutations. We need to have a plan and the vaccine supports that plan, but it's just your plan."