“London is the engine of this country’s economy and my central London constituency is suffering hard,” Ms Buchan told Health Secretary Matt Hancock in the House of Commons.
“As of Friday, London has a substantially lower case rate than the English average, coming in at 75 points lower, and my constituency was 125 points lower.
“Will (Mr Hancock) assure me that London will come out at the lowest tier possible given the health circumstances?”
The latest Government figures show that the seven-day rate of infections had fallen to 197.2 per 100,000 residents by Sunday night, down from a record high of 198.9 on Saturday and 198.3 on Friday.
Mr Hancock replied: “I can assure (Ms Buchan) that London will come out at the tier that is necessary and appropriate based on the public health evidence.”
However, plans to take a “one London” approach have divided authorities after the data laid bare a stark disparity between boroughs.
Havering’s weekly rate of 398 cases per 100,000 was more than three times higher than those of Southwark (116) and Richmond (117).
Pointing to the data, the Tory MP for Harrow East, Bob Blackman, asked how ministers would decide which tier would best suit the capital.
Addressing the Prime Minister, Mr Blackman said: “I understand (Boris Johnson) is going to require London to be in one regional tier.
“But as of the end of last week, the rate of infection in the worst-affected borough was a 372 per 100,000 but in the least-affected area at 125 per 100,000.
“What will drive which tier London goes into, the position in the worst-affected area, the middle or the least-affected area?”
Mr Johnson replied: “(He) will have to wait until the announcements by the Health Secretary on Thursday about exactly who goes into which tier.
“The point about London is that although it’s very diverse and massive (…) it is held together by a very dense mass transit system.”
He continued “Although there are fewer people on it right now, the transmission within London means that it’s quite difficult to separate one bit of London from another.”
Mayor of London, Sadiq Khan, has said he wants the same restrictions to apply to the entire city, but stressed he would continue to analyse the data.
He said in a statement following Mr Johnson’s statement to MPs: “We need to wait and see the final detail of the plan, but it is vital that London’s shops and businesses, which were forced by the Government to close just as preparations for the festive period began, are allowed to open in a safe and Covid-secure manner.
“The Government should also scrap its ill-judged curfew altogether to support our pubs, bars and restaurants.
“While this is certainly not going to be a normal Christmas, it is more important than ever that no-one has to spend it alone. It is important plans are devised to allow people to spend the festive period with loved ones after such a tough year, but this must be done in the safest way possible.
“Given the sacrifices made over recent weeks and months, it will be crucial that the Christmas period doesn’t see a reversal of the progress made in getting on top of the virus – especially when a vaccine is in sight.
He continued: “We will continue to carefully analyse the data over the coming days to determine the tier London should be in on the lifting of the lockdown.
“Londoners should continue to stick to the rules so we do not waste the hard work and efforts that have been made during this lockdown.”