London may need to implement its own visa system in order to retain foreign workers and avoid economic decline post-Brexit, according to a report by the London Chamber of Commerce and Industry, a business network.

As BBC London reports, the 770,000 EU citizens living in London make up 15 percent of the city’s employees. They contribute more than 26 billion British pounds ($32.6 billion U.S.) to the value of goods and services produced in the city, and pay taxes of about 7 billion pounds annually. But thanks to Brexit, research suggests, the city could lose 160,000 migrant workers by 2020. That departure “would be economically harmful, impacting on various key industries and putting pressure on public funds,” according to the report. The financial and construction industries could be especially hard hit: Foreign workers make up a quarter of the former and a third of the latter.

The British government has not yet clarified what status EU citizens will have in a post-Brexit world, but it’s speculated that they will begin receiving the same treatment as non-EU migrants, who are required to have firm job offers and meet minimum salary levels.

The London Chamber of Commerce and Industry recommends instead the imposition of a London work visa, which would grant the right to remain to all current EU workers. It also suggests creating a system of “capital work permits” that allow holders to seek work only in the 33 local authority areas of London and allow the city of London to vary its own levels of migration. Who receives those permits would be partially determined by a shortage occupation list with the goal of attracting talent to certain needed sectors.

Mayor Sadiq Khan has said he is committed to keeping the city open to foreign talent, but not committed to any particular policy measures.