The far-right will seek to exploit the arrival of migrants in the UK on overcrowded boats this year, campaigners said.
The warning from the anti-extremism charity, Hope not Hate, comes after a record number of migrants attempted the perilous Channel crossing from northern Europe to Britain over the past year.
A warmer weather in the UK has led to dozens more trying to cross the Channel – one of the world's busiest waterways.
People smugglers are turning to the sea route because of reduced passenger ferry traffic during the Covid-19 pandemic.
About 100 people were brought into the port of Dover on Wednesday after Border Force vessels intercepted boats attempting to cross the Channel on the warmest day of the year so far, the Daily Mail reported.
Home Secretary Priti Patel set out plans for an overhaul of the immigration system last week, to make it harder for asylum seekers to stay permanently in the country.
Anti-extremism charity Hope not Hate issued a warning that the end of lockdown could lead to a surge in far-right activity after a period of online recruitment.
"People in the far-right are already talking about Covid being a problem on the continent brought over by migrants," Joe Mulhall, a researcher with Hope not Hate, said.
A key far-right theme is likely to be this “talk of invasion and them bringing disease” during 2021, he said.
Under the proposed new plans, only migrants who arrive in the UK through official channels, such as refugee schemes in war zones or escaping persecution, will be entitled to stay in the country permanently.
Britain wants to reduce the number of ways in which people can claim asylum and give only temporary permits to migrants arriving from safe nations.
People who arrive in southern England after crossing the Channel from northern France, would only be eligible for "temporary protection status", under which they would be reassessed for removal at a future date.
A record 8,400 asylum seekers tried to cross the English Channel last year.