Birmingham's covid outbreak has been blamed on families meeting up at home instead of pubs and restaurants where strict measures are in place - as new lockdown rules are due to be brought in.
Dr Justin Varney, Director of Public Health in Birmingham, said the city was facing a number of small clusters caused by people meeting in each others' homes and forgetting to social distance.
He spoke on BBC Radio 4's Today programme alongside the Leader of Leeds City Council Judith Blake.
From Tuesday, more than 1.5million people in Birmingham and neighbouring Solihull and Sandwell will be banned from mixing with anyone outside of their own household in private homes, pubs, restaurants or in gardens.
Dr Varney said: 'The passage of transmission we're seeing across the city and in neighbouring areas is that this is about people meeting up behind closed doors where there aren't covid risk assessments in place and sadly as they pass the biscuits they're passing covid with it.'
The move follows two days of crunch talks between the Government and local health leaders after Birmingham's seven-day infection rate rose to 78 cases per 100,000.
It's difficult to compare Birmingham's current case rate now to levels at the height of the pandemic because there was a lack of widespread testing during the first wave - meaning thousands of cases went missed and never appeared in the data.
People around Birmingham city centre yesterday before the Government announcement brought in tighter lockdown restrictions for the area following a surge in Covid-19 cases
Dr Justin Varney (left), Director of Public Health in Birmingham, said the city was facing a number of small clusters. He spoke on BBC Radio 4's Today programme alongside the Leader of Leeds City Council Judith Blake (right)
Cllr Blake added that she thought it was young people who were to blame for the rising number of cases in Leeds - adding the 'rule of six' meant police would be better able to enforce restrictions and prevent a rise in house parties. Pictured, revellers in Leeds last night
Dr Varney explained social distancing measures in pubs and restaurants meant people kept apart and rigorous cleaning regimes were in place.
Meanwhile, in people's homes they tend to forget about the virus in favour of a handshake or a hug.
'It's so easy to do, to make that mistake and sadly give covid as well as the love and friendship you're trying to share,' he added.
Leeds yesterday avoided further Covid-19 restrictions as it was announced the city would instead receive enhanced support towards managing the rise in infection rates.
Cllr Blake said she thought it was young people who were to blame for the rising number of cases in Leeds - adding the 'rule of six' meant police would be better able to enforce restrictions and prevent a rise in house parties.
She told the Today programme: 'Our numbers of cases are spreading among young people and it's really scattered across the whole of the Leeds district.'
Official PHE figures show Birmingham's case rate was less than 30 per 100,000 by the end of August but this has soared to 78 per 100,000 in less than a fortnight
Britons have promised to run riot and enjoy one last knees-up with friends before Boris Johnson 's stringent new coronavirus restrictions come into force on Monday
A woman walks around Birmingham city centre today wearing a mask as it was announced the area will be put back into lockdown from Tuesday
From Tuesday, more than one million people in Birmingham will be banned from mixing with anyone outside of their own household
People gather outside the The Shipwrights Arms near London Bridge on Friday for a final weekend of freedom out before the new rules hit
People gather at More London Place near London Bridge in London for one more weekend of freedom before the government implements its new rule of six from Monday
Revellers dance on the street as a band plays in front of shops in Leeds during one of the last big nights out in the city before new rules on groups are introduced on Monday
She said bringing restrictions into law on Monday would 'help us with the enforcement with the additional capacity to issue fines'.
'Police colleagues are making their own case but in terms of what were seeing in Leeds we have a large number of srudents back.
'There's been a massive spike in house parties. the ability to fine in those situations will focus their minds on the seriousness of the issue.'
Yesterday, a council spokeswoman said the new rules meant the city would move up one stage from being placed on the national Public Health England watchlist last week as an area of concern.
The seven-day rate of infection now stands at 66 per 100,000 people, with a test positivity of six per cent.