Citizens and permanent residents are not affected.
The decision, which passengers first learnt about yesterday, is likely to affect many Kiwis hoping to fly home.
The new strain has left the United Kingdom in chaos and while the country's chief medical officer said there was no evidence to suggest the new strain caused a higher mortality rate or affected vaccines, it has seen a growing list of European Union nations banning travel from the UK.
London and southeast England — about one-third of the English population — were currently at the highest level of a three-tier system of rules and will be placed in a new tier-four level.
People will be required to stay at home except for essential reasons such as work, and non-essential retail will close, as will indoor leisure and entertainment.
The new strain has also been confirmed as the same one which caused an outbreak in Sydney, creating panic in New South Wales.
The airline states that the decision affects passengers with a travel history to the United Kingdom within the past 14 days.
"This will also apply to long-term pass holders, short-term visitors, and all those who had obtained prior approval for entry into Singapore.
"Singapore Airlines customers with bookings for flights departing from the United Kingdom with effect from 23 December 2020 will be affected by this new requirement."
Instead, affected passengers are being offered a refund.
"Please be assured that customers departing from the United Kingdom who had their flights cancelled or who no longer will be able to travel as they do not meet the entry requirements into Singapore will be covered by our Global Waiver Travel Policy.
"They may retain the value of their ticket as flight credits, rebook or seek a refund. For customers who booked directly with Singapore Airlines, they may use our Assistance Request Form to submit their request."
Bookings made through travel agents were also covered by its travel waiver policy.
"The health and safety of our staff and customers remain our utmost priority. SIA will continue to employ stringent health and safety measures to safeguard our customers' wellbeing.
"We will continue to monitor the situation and remain guided by the regulatory authorities."