More migrants are hiding in lorries and sneaking onto ferries to reach Britain amid a crackdown on small boat smuggling gangs, ministers have been warned.
The Refugee Council said efforts to break the organised crime networks will lead to an "inevitable" shift in tactics.
Charity bosses pointed to a steady stream of asylum applications coinciding with a drop in Channel migrant arrivals.
In the year to June, 97,107 people claimed asylum, down from 102,371 in the year to June 2023.
Over the same time period, 31,493 migrants crossed the Channel in a small boats, down from 44,460 when figures are compared using like-for-like Home Office figures.
The department does not publish numbers for those believed to have been caught arriving in lorries.
The Refugee Council added that small boat arrivals are accounting for a smaller proportion of overall asylum claims.
The charity's chief policy analyst, Jon Featonby, said: "We think, from our experience, one of the key reasons could be that people are changing the way they are arriving in the UK.
"Because that journey is becoming harder, more dangerous, it could be more people are arriving by other means, it could be lorries.
"It's very clear when people arrive by small boat because everybody gets picked up. So it is recorded. We don't know that [for lorries].
"Generally, what we see is people are still trying to reach the UK and they are taking other routes to get here."
Pressed on the shifting tactics of smugglers, Enver Solomon, chief executive of the Refugee Council, said: "It is no secret that where you ramp up enforcement activity, in relation to one route, not just enforcement activity close to the UK border, but all the way further back in Europe, you are going to see a shift in how people seek to get to the UK.
"Displacement is an inevitable consequence of particular enforcement activity. As a consequence, people smugglers seek to adopt other tactics and try to divert to different routes.
"Backs of lorries, arriving clandestinely on ferries, other vehicles. Lorry drops were the main mode of people being brought in by people smugglers prior to the use of boats across the Channel.
"We don't have data. But the assumption is, where the number of asylum applications is holding up, there will be some displacement."
But on Wednesday Downing Street was forced to insist the Government is "committed" to ending the use of asylum hotels amid claims the Home Office is considering reopening some previously closed by the Conservatives.
Labour vowed in its manifesto to stop housing migrants in taxpayer-funded hotels but stands accused of seeking to use more.
Shadow Home Secretary James Cleverly said: "The last Conservative government closed 150 asylum hotels and had flights ready to go to Rwanda.
"But Labour scrapped our deterrent on day one and are now reopening asylum hotels costing upwards of £4million every day - and breaking yet another promise they made to the British people."
The Home Office is understood to be reviewing the hotels being used to house asylum seekers. But the department would not confirm if it was seeking to use more or reopen any of those previously closed.
The Prime Minister's official spokesman said: "As the Government has said previously, we inherited an asylum system in chaos, with tens of thousands stuck in a backlog as people were actively not processed by the previous government.
"What we are doing is surging returns and processing the backlog. We've redeployed 300 staff, we've returned 3,600 individuals with no right to be here.
"Clearly, this is going to take time, and we regularly review our use of asylum accommodation because, as set out in the manifesto, we're committed to ending the use of asylum hotels and saving the taxpayer billions of pounds."
A Home Office source said Labour "inherited a chaotic landscape of expensive hotel contracts, large sites and dispersed accommodation", adding: "We have started processing asylum claims, which had ground to a halt under the Tories, leading to a record asylum backlog and a £5billion black hole in the Home Office budget.
"The Home Office regularly reviews our asylum accommodation footprint to reduce costs, build flexibility and deliver value for money for taxpayers."
More than 27,000 migrants have arrived in the UK after crossing the Channel so far this calendar year.
Home Office figures show 176 arrived in three boats on Tuesday, taking the provisional total for 2024 to date to 27,509.
This is up 6% on this time last year (25,931) but 26% down on the same period in 2022 (37,099).
Since Labour won the General Election in July, 13,935 arrivals have been recorded - lower than the equivalent periods last year and in 2022.
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