SINTRA, Portugal (Reuters) - The European Central Bank's ability to respond to a major economic downturn resulting from Britain's departure from the European Union is limited, so other authorities would have to step in if it happens, the ECB Vice President said on Wednesday.

"In monetary policy, we still have instruments," Vitor Constancio told a conference in Sintra, Portugal.

"But it’s true that we have been using quite a lot of those instruments, we are aware and everyone is aware.

So, if the consequences (of Brexit) would be more severe in economic terms, what could be done, if anything? But it’s with other authorities, it’s not then with the ECB."

(Reporting by Balazs Koranyi and Francesco Canepa)