The official campaign for Britain to leave the European Union has complained to police about an advertisement by Ryanair that offers expatriate Britons cheap tickets to come home and vote to stay in the bloc.

The Irish airline has been actively campaigning for Britain to stay in the EU, spending €25,000 (£19,269.5 or Dh103,062) on adverts urging customers to vote “In” and warning that it might withdraw some investment from Britain if “Out” voters win.

In a “Brexit special” advertisement, Ryanair said British voters overseas could fly home to vote “Remain” for €19.99 on the day of the referendum, June 23, or the day before. The tongue-in-cheek ad doesn’t suggest Ryanair has any way of knowing how passengers would vote, if at all.

Vote Leave, the official Brexit campaign, wrote to London’s Metropolitan Police complaining the special offer may violate referendum rules and anti-bribery laws.