[3] The agency came under formal criticism from the Parliamentary Ombudsman for consistently poor service, a backlog of hundreds of thousands of cases, and a large and increasing number of complaints.

Overseas staff vetted visa applications and operated an intelligence and liaison network, acting as the first layer of border control for the UK.

[13] Founding Chief Executive Lin Homer left the agency in January 2011 to become the Permanent Secretary at the Department for Transport.

Home Secretary Theresa May announced to Parliament on 26 March 2013 that the agency would be abolished due to continuing poor performance, and replaced by two new smaller organisations which would focus on the visa system and immigration law enforcement respectively.

[15] The UK Border Agency occasionally removed foreign national criminals at the end of their prison terms.

The CTA is an intergovernmental agreement that allows freedom of movement within an area that encompasses the UK, Isle of Man, Channel Islands (Guernsey, Jersey, Sark and Alderney) and the Republic of Ireland.

The assessment of the Independent Chief Inspector, carried out between July and August 2010, found that there was an inconsistent response towards applications, with some cases given extra time to prepare and others dismissed for minor reasons.

[17] In November 2011, the Home Affairs Select Committee issued a report that found that 124,000 deportation cases had been shelved by the UKBA.

The report said the cases had been dumped in a "controlled archive", a term used to try to hide the fact from authorities and auditors that it was a list of lost applicants.

[18] Following allegations that staff were told to relax some identity checks, in November 2011 the UK Home Office suspended: Brodie Clark, the Head of the Border Force;[19] Carole Upshall, director of the Border Force South and European Operation;[citation needed] Graham Kyle, director of operations at Heathrow Airport.

[19] A two-week inquiry led by former Metropolitan Police detective Dave Wood, currently head of the agency's enforcement and crime group, sought to discover to what extent checks were scaled down, and what the security implications might have been.

It was then announced on 5 November by Theresa May that an independent inquiry would also be undertaken, led by the Chief Inspector of the UK Border Agency, John Vine.

[23] In October 2014, the trial of the Reverend Nathan Ntege – accused of conducting almost 500 sham marriages at a church in Thornton Heath, South London between 2007 and 2011 – collapsed after it became apparent that evidence had been tampered with, concealed, or even possibly destroyed.

As immigration officers were questioned in the witness box of the Inner London Crown Court it became clear that not only had video footage gone missing but that an investigation log had been tampered with.

The trial was halted by Judge Nic Madge, who said in court: "I am satisfied that officers at the heart of this prosecution have deliberately concealed important evidence and lied on oath.

The Reverend Ntege and six other defendants were formally acquitted of all 17 charges, which related to marriages of convenience in order to bypass immigration laws.

Channel 4 News later reported that three immigration officers had been suspended and that the Independent Police Complaints Commission (IPCC) would be conducting an investigation.

[24] Despite the collapse of the 2014 criminal case, in 2019 a Church of England disciplinary panel removed Ntege from his office and from the priesthood over complaints concerning marriages, their administration, and the improper retention of funds.