"My message to them is clear: you are Londoners, you are welcome here and you deserve a commitment from the Government that you can stay," Khan was quoted as saying in the press release.
Khan stressed that it was unacceptable to make people who had contributed to the city of London and the country in general worry about their future, adding that it was crucial to protect EU citizens living in the United Kingdom.
The mayor called on the Home Office to launch "a separate simple process" for all EU nationals staying in the United Kingdom on the legal basis to apply for permanent residence.
On Monday, the House of Commons rejected an amendment to the Article 50 of the EU Treaty, guaranteeing the right of EU citizens to remain in the country post-Brexit. The decision triggered harsh criticism and protests.
Earlier in the day, Queen Elizabeth II gave her royal assent to the bill on the notification of withdrawal from the European Union, changing its status into a law. The royal approval allows May to trigger Article 50, officially starting Brexit negotiations.