If the festive season can sometimes involve trolling relatives with different political views, Sadiq Khan has arguably taken the tradition to a grand scale with a New Year’s Eve fireworks display which has prompted apoplexy among Brexiters with its pro-EU message.

The mayor hailed the event, in which the London Eye was lit up in the blue-and-yellow colours of the EU flag, as part of a wider message to Europe that the capital would stay “open-minded” and “outward looking” after Brexit.

As the fireworks went off along the Thames, the words “London is open” were said in English, French, German, Italian, Polish, Romanian and Spanish just after midnight.

The phrase is often used by the Labour mayor, who opposes Brexit and has called for a second referendum. The event also featured musical performances by European artists.

“We, in my opinion, are one of the greatest cities in the world; one of the reasons we are one of the greatest cities in the world is because of the contribution made by Europeans,” Khan said before the display. “I think diversity is a strength and I think what tonight is about is celebrating that diversity.

“I hope that members of parliament, members of the government will see the fireworks tonight, will listen to the soundtrack and will reflect on what sort of country they want to live in post-March.”

He said the display was about “showing the world, while they’re watching us, that we’re going to carry on being open-minded, outward looking, pluralistic”.

In a tweet afterwards, the mayor said: “Our 1 million EU citizens are Londoners, they make a huge contribution, and no matter the outcome of Brexit, they will always be welcome.”

While the sentiment might be popular with many Londoners, given the capital voted strongly in favour of staying in the EU, the display brought condemnation from the more militant Brexiters.

Andrew Bridgen, a Conservative MP with an occasional sideline in Brexit-based hyperbole, said the message had been “a betrayal of democracy”, telling the Sun: “It’s low, it’s very low to politicise what is an international public event.”

Roger Helmer, a former Conservative MEP who defected to Ukip, tweeted: “While the UK is locked in critical negotiations with Brussels, Sadiq Khan chooses to display the other side’s flag on the London Eye. Would he have shown an Argentinian flag during the Falklands war?”

The anti-Brexit message is in keeping with Khan’s wider views on Brexit, where his public expressions are notably different from the pledges to respect the verdict of the 2016 referendum made regularly by the Labour leader, Jeremy Corbyn.

Khan, who took over the mayoralty from Boris Johnson and plans to stand for another four-year term in 2020, has argued for a special Brexit deal for London, to protect both the contribution of its high population of EU nationals, and the financial institutions of the City.

In September, Khan said the time wasted by Theresa May and the risk posed by a no-deal Brexit meant he was supporting a second referendum, which should include the option of staying in the EU.

The mayor has previously annoyed political opponents with symbolic gestures, most notably his decision to allow protesters against the visit of Donald Trump in July to fly a “Trump baby” balloon mocking the US president, with whom he has previously clashed over Trump’s response to terror attacks in London.

A large-scale fireworks display on the Thames has gradually become a regular part of London’s New Year’s Eve celebrations since one was organised for the millennium celebrations.