A no-deal Brexit would have "vast" consequences for culture in the UK, according to representatives from the sector, putting future funding and touring at risk, and cutting off access to staff, research and networks.
The government would be highly unlikely to replace EU funding for museums and the arts in the event of a no-deal Brexit, warned Bernard Donoghue, the director of the Association of Leading Visitor Attractions.
Museums would also lose access to a European network of workers, curators and programmers, he said.
Donoghue told Museums Journal he is "not optimistic in the slightest" that lost EU funding would be replaced following a no-deal departure, adding: "The economic consequences of that for the entire economy, let alone the cultural economy, would be absolutely vast."
"All museums and galleries in the UK have really benefitted from being able to access EU cultural funding, whether that's in terms of supporting temporary exhibitions or touring exhibitions or bringing together a network of workers, curators or programmers," he said.
Donoghue, who says he has raised concerns about EU funding with the Department for Digital, Culture, Media and Sport, said: "It is their intention that they do [replace funding] but they haven't set sums as to what that might be."
Asked about the implications of no-deal, an Arts Council England spokeswoman said: "Over two-thirds of our funded organisations work internationally and in the event of a 'no-deal' Brexit many would feel the impact immediately.
"The range of issues include staff and artists requiring visas; equipment needing carnets and exhibitions needing licences to tour; in addition to increased costs relating to working or touring overseas."
Donoghue warned that Northern Irish visitor attractions would be particularly affected if a no-deal Brexit led to the creation of a hard border with Ireland, noting that 40% of visitors to Northern Ireland come from the Republic.
"Requiring a hard border, checking passports, customs checks, would have a seriously detrimental effect on the Northern Irish visitor economy, which has just bloomed in the last 20 years since the Good Friday Agreement," he said.
The Irish Tourism Industry Confederation warned last month that a no-deal Brexit would be a "doomsday scenario" for tourism in the country, costing the sector around €260m (£232m) in the immediate aftermath and up to €500m in lost revenue in subsequent years.
The cross-border tourism body added: "It would appear that, irrespective of a 'deal' or 'no deal' between the UK and the EU over the coming months, the impact on the sector will not be without cost."
An additional impact would come if entry to the UK from the EU required visas or an American-style Electronic System for Travel Authorisation (Esta) after Brexit, Donoghue added.
He said: "We know that every time the UK has imposed a visa or Esta-type requirement to come to the UK, leisure visitors in particular have dropped off a cliff almost immediately."
The prospect of the UK leaving without a deal in place appears to have grown in recent weeks, with the trade minister Liam Fox putting the likelihood at 60%.
Donoghue confirmed that UK cultural institutions are already being excluded from EU funding initiatives in anticipation of Brexit, citing the London International Festival of Theatre, for which he chairs the board of trustees, as an example.
Brexit day is scheduled for 29 March 2019.