Scientists warned ministers that the public would start ignoring lockdown rules if they even suggested they would be lifted, new documents have revealed.
And ministers were told allowing people to set up 'support bubbles' could have a "large effect" on the epidemic.
The advice came two weeks after Boris Johnson sparked headlines and confusion after declaring he wanted to "get going" on easing lockdown measures.
Sage, the government's coronavirus advisory body, told ministers the risk of making multiple changes to the rules at the same time was "significant."
And they warned "overall public adherence with social distancing measures will likely be diminished by [the Government] signalling its intent to release even some of the measures."
The advice came in a meeting held on May 21, 2020.
Two weeks earlier, Mr Johnson had told MPs he wanted to "get going with some of these measures on Monday".
Downing Street scrambled to play down reports of an early release from lockdown - after newspapers declared "Happy Monday" and welcomed the promised "freedom".
The meeting minutes also warned the public response to government making multiple changes to lockdown rules at the same time was "highly unpredictable."
The minutes read: "Sage considered that the behavioural responses in the event of multiple, simultaneous changes to current restrictions were highly unpredictable and that the possibility of large, unintended, negative consequences with respect to adherence to remaining measures was significant."
The group also advised either social bubbling or reopening primary and secondary schools risked recreating "significant transmission networks, which would have a large effect on the epidemic."
Support bubbles - where two households can join together without social distancing - were announced on June 10, and introduced last Saturday.
