LONDON (Reuters) - Activist Crystal Amber on Monday disclosed a 3.11 percent stake in De La Rue, the company that makes British passports, in a filing to the London Stock Exchange.

Crystal Amber had taken a stake in De La Rue earlier this month after it lost the contract for Britain's new blue post-Brexit passports to Franco-Dutch firm Gemalto, Sky News previously reported.

De La Rue's current contract, which is worth 400 million pounds, ends in July 2019.

(Reporting by Maiya Keidan; editing by Simon Jessop)