The report found that government departments spent a collective $5.8 billion and mobilised 22,000 employees between the June 2016 vote and the Brexit date.
A tendency for secrecy in the Department for Exiting the European Union (DExEU), a department set up to specifically to prepare for Brexit, hampered the movement of information across departments, the report went on to detail.
"DExEU kept a tight hold on communications, keeping secret anything which might pertain to the UK’s negotiating position… this instinct for secrecy in government can get in the way of effective coordination, collaboration and a sense of urgency in progressing towards a common goal", the report said.
The spending watchdog also called out the frequency of issuing non-disclosure agreements to key employees, which it says "undermined transparency and hampered the spread of information to the business community at large".
The UK is currently in a transition phase which is set to run to the end of the year. Negotiations on a range of matters, from trade to borders, are currently underway between London and Brussels.
The Brexit vote has proven a key moment in the UK’s modern history. It was followed by years of political chaos in London and an increasingly polarized public sphere.