Speaking at the government’s daily coronavirus briefing, Dr Jenny Harries added: “This is not to say we would be in complete lockdown for six months.”
But, she continued, the UK had to be “responsible” in its actions and reduce social distancing measures “gradually”.
It comes as the number of people in the UK to have died with coronavirus reached 1,228.
Among those to have died with the virus is Amged El-Hawrani, a 55-year-old doctor and ear, nose and throat trainer at Queen’s Hospital Burton. His death was confirmed shortly before the press briefing. An organ transplant consultant died last week.
Dr Harries said the government would review the lockdown measures for the first time in three weeks.
But she warned the public: “We must not then suddenly revert to our normal way of living. That would be quite dangerous.”
She continued: “If we stop then all of our efforts will be wasted and we could potentially see a second peak.
“So over time, probably over the next six months, we will have a three-week review. We will see where we are going.
“We need to keep that lid on – and then gradually we will be able to hopefully adjust some of the social distancing measures and gradually get us all back to normal.
“Three weeks for review, two or three months to see whether we have really squashed it but about three to six months ideally, and lots of uncertainty in that, but then to see at which point we can actually get back to normal.”
But Dr Harries also said it was “plausible” that it could further than that.
On the number of deaths from the virus, she added: “We actually anticipate our numbers will get worse over the next week, possibly two, and then we are looking to see whether we have managed to push that curve down and we start to see a decline.”
Meanwhile, Housing Secretary Robert Jenrick said the UK was on “emergency footing” in a way “unprecedented” in peacetime.
Giving an update on the measures in place to get personal protective equipment to frontline NHS staff, Mr Jenrick said there was now a “national supply distribution response team” to deliver PPE to those in need, supported by the Armed Forces and other emergency services.
Some 170 million masks and almost 10 million items of cleaning equipment are among the items being delivered to “58,000 NHS trusts and healthcare settings”, he said
“We haven’t done anything like this since the Second World War,” he added.