Homelessness surged this year to the highest level on record, the federal government reported on Friday.

An annual head count, conducted in January, found the homeless population had increased by more than 70,000 people, or 12 percent. That is the largest one-year jump since the Department of Housing and Urban Development began collecting data in 2007, and the increase affected all parts of the homeless population.

Biden administration officials and academic experts said the increase reflected both a sharp rise in rents and the end of the extraordinary measures the government had enacted during the pandemic, including emergency rental aid and bans on eviction.

“The most significant causes are the shortage of affordable homes and the high cost of housing,” said Jeff Olivet, head of the United States Interagency Council on Homelessness.

Since the start of the pandemic, the cost of basic shelter has risen more than 20 percent, according to federal estimates called fair market rents.

But some researchers said that the rise in homelessness also stemmed from the growing number of migrants entering the homeless services system. That trend has only intensified since the count was taken, as Republican governors, especially Greg Abbott in Texas, have sent more people who have arrived from across the border to Northern cities.

Some of the sharpest growth in homelessness has occurred in the cities most affected by the influx of migrants, including New York, Denver and Chicago.

“Even without the migrant crisis we would have seen some increase, but certainly not to this extent,” said Dennis Culhane, a professor at the University of Pennsylvania who has long served as an adviser to the federal government’s annual count.

“This is partly a manufactured problem,” he added, because the migrants could have been treated outside more humanely outside the homeless services system in areas where they had arrived.

By the government’s count, 653,104 people in the United States were homeless in January.

Homelessness grew among every group the federal government tracks. It rose among individuals and families with children. It rose among the young and the old. It rose among the chronically homeless and those entering the system for the first time.

It also rose among veterans, the group that in recent years had experienced the sharpest declines, after a significant expansion of federal aid.

The report coincides with increasingly sharp political clashes over homelessness and is likely to quicken the debate between progressives who seek more aid and conservatives who seek stricter programs and policing.

Many communities have tried to clear encampments or ban outdoor sleeping. Leading Republicans rallied to the support of a New York man arrested in May for killing a homeless passenger on a subway train. Former President Donald J. Trump, who is seeking a return to office, has said he would force the homeless into urban camps.

Other Republicans have criticized the federal policy of giving homeless people housing without requiring them to be treated for addiction or mental health issues, an approach called “Housing First.”

But supporters of the policy, which long drew bipartisan support, say rigorous evidence has shown that it saves lives. They argue that the system needs more money, especially for housing.

“What I don’t want to see happen is people pointing to this count and saying the homeless system doesn’t work,” said Ann Oliva, who runs the National Alliance to End Homelessness, an advocacy group. “The biggest driver of these numbers is the lack of affordable housing.”

A growing body of research has shown that growing rent burdens lead to increased homelessness. Federal housing aid reaches only about one in four eligible households, and the share of households who pay more than half their income for shelter is at a record high.

From 2007 to 2016, homelessness fell every year, by a total of 15 percent. It then rose by about 6 percent in the years before the 2020 coronavirus pandemic. The one-year rise of 70,000 in 2023 is more than four times greater than any previous increase.

“Rents went up in lots of places during the pandemic, but we prevented a massive dislocation, largely due to the moratorium on evictions,” said Gregg Colburn, a professor of real estate at the University of Washington. “Without a significant policy response, this problem will continue to get worse.”

President Biden ran on a pledge to extend housing aid to all who qualify but has won little permanent new assistance from Congress.

In arguing that migration is driving the numbers — or, more precisely, the diversion of asylum seekers into the homelessness services system — Mr. Culhane points to their location.

Nearly three-quarters of the growth occurred in five states, of which four have been heavily affected by the migration crisis. They are New York, Florida, Colorado and Massachusetts. New York alone accounts for more than 40 percent of the growth. (California is the fifth state.)

In addition, Mr. Culhane notes, about 55 percent of the growth in homelessness occurred among people who identify as Latino. The annual count does not ask people if they are migrants.

“This isn’t the natural flow of migration — this is the intentional relocation of migrants to communities not prepared to handle them,” he said.

At the same time, sharp increases in the numbers of homeless veterans (up 7 percent) and chronically homeless people (up 12 percent) suggests other forces must be in play, because a recent surge in migration would not affect either group.

“Something else is going on,” said Margot Kushel, director of the Benioff Homelessness and Housing Initiative at the University of California, San Francisco, who said inflation may be a factor. “If your income was steady and all your expenses went up, that is the same as a rent increase.”

Kevin Corinth, an economist at the conservative American Enterprise Institute, said he was especially concerned about the 10 percent rise in unsheltered homeless people — those living on the streets — a condition that carries high risk of injury or death. He noted it had risen every year since 2015, with the numbers especially high in western cities, which have fewer laws banning people from living on the streets.

While high rents are part of the problem, he said, the continual rise of people living on the street is “in part an indictment of the homeless services system,” which he called expensive and ineffective.

To the extent the number also reflects the migrants’ presence, he noted, it is likely to rise, since that population has grown since the count was taken nearly a year ago.