An official wrote: "I have been asked to canvas opinion on the level of support for immediate roll out of the Winter Plan – Plan B."
It lists a "menu of measures" including introducing vaccine passports in nightclubs, crowded indoor settings and outdoor venues with more than 10,000 attendees that could be brought in by ministers.
There would also be the need for "legally mandating face coverings in certain settings" under plans being considered.
The message adds that the public would have to be told "clearly and urgently" that the risk level had increased with "the need to behave more cautiously".
This would include measures such as working from home.
Local authority chief executives and council leaders were asked whether they "supported" Plan B with responses being fed into the Cabinet Office.
But Conservative MP Mark Harper, chair of the Covid Recovery Group, last night said: "This leaked memo directly contradicts the assurances given by ministers only a few days ago.
"Our vaccines work, Covid will be with us forever and we must start to live with this virus as ministers have suggested.
"If we shut down the economy to manage pressures on the NHS this year, then restrictions will become a seasonal event every year in the future.
"There are no 'low cost' Covid restrictions. Plan B would herald the beginning of the end for many businesses across the country. Ministers need to get a grip."
It comes after Prime Minister Boris Johnson said the current high levels of cases weren't outside the "parameters" of predictions for the autumn and winter.
Shadow Health Secretary Jonathan Ashworth said: "With a mounting tide of Covid sickness and hospitals under crushing pressure it's no surprise Tory ministers are secretly plotting to bring back masks and introduce vaccine passports.
"But whether it's plan A, B or C to get on top of this deadly disease Sajid Javid needs to urgently fix the stuttering jabs campaign.
"Vaccination should be our wall of defence but that wall is crumbling. The complacency must be ditched, we need vaccination fixed."
A UKHSA spokesman said: "We don't comment on leaks. It is part of UKHSA's role to provide advice to the Government on the ongoing response to the pandemic.
A government spokesman said: "We knew the coming months would be challenging – this is exactly why we set out our Covid Plan for Autumn and Winter.
"We are monitoring all the data closely, and the Prime Minister has been clear that it does not yet show that Plan B is necessary.
"Our focus remains on our booster campaign, vaccinating 12-15 year olds, and encouraging those who haven't yet come forward to have their jab.
"But it is ready should we need to act to avoid a rise in hospitalisations which would put unsustainable pressure on the NHS."
