More than 3,000 asylum seekers could be detained and deported from the UK every month to enforce Suella Braverman’s flagship asylum bill, leaked documents show. As Rishi Sunak faced a backlash from Conservative MPs over record levels of net migration, briefing papers have revealed the government has drawn up plans to remove 3,163 asylum seekers every month from January. The documents, which focus on the implementation of the illegal migration bill, also make clear ministers could face crippling legal action without a substantial increase in legal aid fees for lawyers who advise refugees. It is the first detailed glimpse of the scale of the task facing Whitehall if it is to implement Braverman’s bill, which is currently before the Lords. The Home Office has until now refused to release the impact assessment of the bill. The disclosure came as net migration and the backlog of asylum claims reached record highs. The prime minister was forced to concede that numbers should come down after figures from the Office for National Statistics showed overall migration into the UK for 2022 was 606,000, which represents a 24% increase on the previous high of 488,000 last year. More than 100,000 people seeking asylum have waited longer than six months for an initial decision on their case, the latest figures showed, while more than three-quarters of all small-boat asylum applications since 2018 are still awaiting a decision. The leaked documents, marked “urgent”, were prepared this week for Alex Chalk, the lord chancellor, the junior justice minister Lord Bellamy and the Ministry of Justice permanent secretary, Antonia Romeo. The aim was to ensure there were enough lawyers on hand to provide advice at immigration detention centres if the bill passes into law. Under the bill, those who arrive in the UK without permission will not be able to stay to claim asylum but will instead be detained and removed, either to their home nation or a third country such as Rwanda. The documents, prepared using data from the Home Office, say the department should prepare for 1,600 people to be held under the bill in detention centres from September, rising to 3,163 every month from January. One document said: “Steers are required as soon as possible to engage legal aid provider and – if you agree it is necessary – start implementing fee increases in time for September 2023 when we are expecting to provide access to legal aid to 1,600 individuals (scenario B) and scale to 3,163 individuals a month (scenario C) from January 2024.” Enver Solomon, the chief executive of the Refugee Council, said the documents show that the government, contrary to its claims, is preparing for mass deportations. He added: “While the government has been rigorously sticking to the line that its new bill would ‘act as a deterrent’, this information shows that it is well aware that vulnerable people will keep arriving in the UK in search of protection. “It is appalling that it is preparing to lock up and kick out thousands of men, women and children, most of whom would be found to be refugees if their claim was heard on UK soil.” In the documents, civil servants recommend increasing legal aid fees by at least 15% in order for the government to be able to attract solicitors to represent thousands of asylum seekers. But the document also puts forward a possible increase of 200%, which is not recommended. Chalk is warned by civil servants that a judicial review could be launched if he fails to provide legal advice to detainees. The briefing said: “You (lord chancellor) will have a statutory duty to secure that legal aid is available to this cohort … Not addressing capacity issues could mean that there are not sufficient legal aid providers to carry out this work. This could be challenged by way of judicial review.” According to one document, current hourly rates for immigration solicitors are between £53 and £74. Civil servants held a meeting with specialist firms in the sector who “were clear that unless legal aid rates are substantially increased they would not be able to justify allocation of IMB work in any volume over privately paid casework,” the document said. Assuming that ministers approved of an increase in fees, the document recommended a 15% increase to up to £86 an hour, which would result in an increase in expenditure on fees from £53m to £61m a year. Under the heading of “financial implications”, civil servants warned that the option of paying lawyers more is “unfunded”. “We would need to seek assurance and agreement from HMT [the Treasury] and HO [Home Office] to increase fees,” the document said. An MoJ source said the document, which was circulated among dozens of civil servants, is a draft which has not been seen by ministers or Romeo. A Ministry of Justice spokesperson said: “We do not comment on leaks.” The net migration figure, which is the difference between the number of people moving to the UK and the number leaving, is up from 488,000 in 2021. The estimates include people who have come to the UK from Ukraine and Hong Kong under resettlement schemes, as well as overseas students. The Conservatives’ 2019 manifesto promised that “overall numbers will come down” as the government ended freedom of movement from the EU in the wake of Brexit. Tory MPs warned of voter anger and frustration at “unsustainable” levels of net migration. Aaron Bell, the MP for Newcastle-under-Lyme, said the figures were too high and his voters would “expect to see them fall”, while Louie French, the MP for Old Bexley and Sidcup, said the “unsustainable levels of migration” were having a “significant impact” on housing. Newly released figures showed that more than three-quarters of all small-boat asylum applications since 2018 are still awaiting a decision. Charities said the human cost of such delays is “staggering”, but the immigration minister, Robert Jenrick, appears to suggest that processing claims at a quicker pace could lead to an increase in people claiming asylum. He told MPs: “It is not correct, however, to suggest that if you can process illegal migrants’ claims faster that that will reduce the number of people coming into the country. In all likelihood it’ll lead to an increase.” Following Jenrick’s comments, Downing Street said tackling the backlog was “the right approach”. The prime minister’s spokesperson said the government was taking steps to reduce the backlog, but said it would take time for these policies to have an effect.