The Department to Exit the EU has seen its workforce of civil servants surge by more than 400% in the space of just two months.
New figures released to the House of Commons show that the ministry, established by Theresa May in the wake of the Brexit vote, now has more than 200 civil servants, up from around 40 in July, with a further 120 officials in Brussels.
A source also told IBTimes UK just "a handful" of the staff are working in the department's press operations, with some being seconded over from other ministries.
Robin Walker, the parliamentary under-secretary of state for Exiting the European Union, described the department as "fast-growing".
Leave campaigner and former Europe Minister David Davis was appointed Brexit Secretary in July as part of May's reshuffle.
The senior Conservative is expected to work closely with the prime minister, International Trade Secretary Liam Fox and Foreign Secretary Boris Johnson on the government's plan to split from the EU.
Oliver Robins, who previously worked at the Home Office under May, has been appointed the permanent secretary for the Department for Exiting the European Union. Sarah Healey serves as director general for the ministry, having worked in a similar role at the Department for Culture Media and Sport.
Healey won the BBC's University Challenge quiz show in 1998 as part of a team from Magdalen College, Oxford University.
The government, meanwhile, has been warned splitting from the EU could be an expensive businesses.
Liberal Democrat MP Tom Brake revealed to MPs that a headhunter told him a top trade negotiator could cost around £750,000 a year – or more than five times the salary of the prime minister (£143,462).
Senior MEP and former prime minister of Belgium Guy Verhofstadt will lead Brexit negotations for the European Parliament, while the European Commission has appointed French politician Michel Barnier and German trade official Sabine Weyand to lead talks, as part of a Brexit taskforce.
Negotiations between the parties will start once the government trigger Article 50 of the Lisbon Treaty, the official mechanism to split from the EU. May has ruled out making such a move this year, but is expected to trigger it in 2017.
The Department for Exiting the EU had not responded to a request for comment at the time of publication.