The spread of coronavirus in the UK could have been slowed with earlier quarantine restrictions on arrivals, a group of MPs has said.
The Home Affairs committee said a lack of border measures earlier in the pandemic was a "serious mistake".
It added ministers had underestimated the threat of importing the virus from Europe as opposed to Asia.
But a Home Office spokeswoman said the committee were "incorrect in their assertions".
She added: "All of our decisions throughout the pandemic have been guided by the science, with appropriate measures introduced at the right time to keep us all safe."
In their report, the committee backed a decision not to close the UK's borders in the early stages of the crisis, given the "large number" of returning British nationals.
But it added that a requirement for people arriving from certain countries to quarantine, introduced in early June, should have come in earlier.
Since then, those arriving in the UK have to self-isolate for 14 days or face the threat of fines, with each of the UK's four nations compiling a lists of exempted countries where this does not apply.
During February and early March, all passengers from China, Iran, South Korea and later Italy were asked to self-isolate for 14 days on arrival.
The MPs criticised a decision not to include Spain on this early list, adding that government advice had initially focused on Asian countries and did not "recognise soon enough" the risk of importing the virus from Europe.
They added that a later decision - on 13 March - to end self-isolation advice for international arrivals not displaying symptoms had been "inexplicable".
Citing evidence from scientific studies, they said it was likely that thousands of infected people then arrived in the UK before full lockdown came in 10 days later.
"It is highly likely that this contributed to the rapid increase in the spread of the virus in mid-March and to the overall scale of the outbreak in the UK," they added.
"The failure properly to consider the possibility of imposing stricter requirements on those arriving - such as mandatory self-isolation, increased screening, targeted testing or enforceable quarantine - was a serious error."
Source: BBC News