The stark warning was revealed in a new report from the Royal Institute of British Architects (RIBA) which laid bare the uncertainty surrounding the construction industry.

Containing the second year’s results from the most comprehensive survey of architects on Brexit, Global by Design 2018 gives an insight into the major priorities and trends facing the profession, revealing significant concerns about a continued lack of clarity on the UK’s future relationship with the EU.

According to the report, more than two thirds (68%) of architects have reported projects put on hold, and more than two in five (43%) architects have seen projects cancelled since the EU referendum (61% had delays, 36% had cancellations in 2017).

Around 71% of architects are concerned that Brexit will have a negative impact on the built environment (60% in 2017), while 74% state that frictionless access to the European single market is a priority for expanding international work.

The number of EU architects who have considered leaving the UK since the EU referendum has significantly increased from 40% in 2017 to 60% this year.

In response to the concerns, the report sets out a series of recommendations for the UK government to maintain and strengthen the UK as a global hub for architecture, including:

RIBA President Ben Derbyshire said: “2018 is a critical year for the UK and whilst our architect members are adaptable and creative, the results from our survey show increasing uncertainty amongst the profession. While the UK government has provided the headlines on the country’s future relationship with the EU, we need urgent action from them if the UK is to stem the talent exodus and inspire confidence in UK construction investment.

“The UK must maintain and strengthen its role as a global centre for architecture, responsible for creating innovative and inspiring buildings and communities in the UK and across the world. But to do this we need the right agreements and conditions in place to ensure that the UK continues to be a global facing nation and an attractive place to live, work and invest. We will be continuing to make this case to government on behalf of our members.”

RIBA chief executive, Alan Vallance, added: “Attracting and retaining skills and talent in the UK is absolutely critical to the architecture and construction sector. We have been working closely with the UK government, stressing the urgent need for progress and clarity on behalf of the architecture profession.

“Whilst our calls for continued mutual recognition of qualifications are being heard, many EU architects continue to face uncertainty about their future in the UK. This is unsustainable: it is having a real-time impact on recruitment and is unquestionably a threat to the success of our economy and society. The UK government must make urgent decisions that allow the sector to thrive today.”