The Royal Institute for British Architects (RIBA) is concerned Brexit and the end of freedom of movement could put the country's £4.8 billion architecture sector in "jeopardy".
One in four architects in the UK are international, 80 per cent of which are from EU countries.
Nearly half of the 600 architects who are non-UK nationals surveyed said Brexit had made them consider leaving their jobs in the UK.
UK risks "cutting itself off from the world"
RIBA's report, Powered by People: Building a Post-Brexit Immigration System for UK Architecture, lays out the case for a more flexible immigration system for skilled workers such as architects.
"Our sector thrives on diversity, benefitting from different ways of working, backgrounds and experience," said RIBA chief executive Alan Vallance.
"Without drastic reform, the UK risks turning inwards and cutting itself off from the world."
The report also highlighted that there had been a 46 per cent drop in the number of EU architects registering in the UK since 2016, when the country voted to leave the EU.
RIBA calls for end to cap on visas
As Brexit draws closer, with the UK scheduled to leave the EU on 29 March 2019, RIBA has asked the government to consider a series of changes to the immigration system.
It called for an end to the annual cap on Tier 2 visas for skilled workers. The report also pointed out that the average starting salary for UK architects of £28,000 is below the threshold for a Tier 2 visa.
In December 2018 the government announced it would allow architects to apply for Tier 1 visas, given to those who can demonstrate "outstanding" talent or potential.
The body also called for flexibility in minimum salary thresholds in visas according to region, a streamlined residency application process, and flexibility for workers to live and travel abroad.
It also recommended getting rid of the immigration skills charge, where practices are charged for every non-UK worker they hire.
Closed borders harms more than economy
Barriers to EU architects living and working in the UK would harm more than just the economy, RIBA also warned.
"In addition to the recommendations laid out in our report, we are calling on politicians to be open about the benefits of migration to our society – it is vital to the success of not just our businesses, but the places and spaces that architects create for our communities," added Vallance.
Leading British architects including Norman Foster, Richard Rogers and David Chipperfield have already written to the government to warn that Brexit will have a "devastating" effect on architecture in the UK.