The asylum backlog has been on an upward trend in recent years, driven by a sharp rise in cases and longer turnaround times for decisions.
A total of 172,758 people were waiting for an initial decision on an asylum application at the end of March 2023, Home Office figures show.
This was up 57% from 109,735 at the end of March 2022 and is the highest figure since current records began in 2010.
Of the 172,758, 128,812 (75%) had been waiting for an initial decision for more than six months.
In March 2022 the number waiting longer than six months stood at 73,207, or 67% of the total.
The Bibby Stockholm barge, which is moored at Portland in Dorset, has been refurbished to accommodate up to 500 asylum seekers.
The first 15 were taken on board on Monday.
The vessel is one of a number of locations intended to house migrants while their asylum applications are being considered by UK authorities.
Other sites include the former Royal Air Force base at Wethersfield in Essex, which received its first occupants in July, and the RAF base at Scampton in Lincolnshire, where plans have reportedly been delayed.
Both sites, which are the subject of legal challenges by local councils, are expected to be able to house nearly 2,000 people.
Asylum seekers are also placed in smaller types of accommodation, such as hotels, or privately-run flats and shared houses.
Some 50,546 asylum seekers were living in hotels in the UK at the end of June 2023, up from 47,518 at the end of March, according to Home Office data.
A further 58,636 were in “dispersed accommodation”, such as flats and houses, up from 56,979.
Separate figures show the number of UK asylum applications – rather than applicants – awaiting an initial decision stood at 136,779 as of July 30, down slightly from 138,052 at the end of March.
One application does not equal one person, as an application can cover several individuals.
The Government has set a target of clearing the backlog of “legacy” applications by the end of 2023.
This refers to applications made before June 28 2022.
The number of legacy applications awaiting an initial decision stood at 62,157 on July 30, down from 80,148 at the end of March.
The number of new applications (made on or after June 28 2022) stood at 74,622, up from 57,904.