Ukip has been accused of “baseless scaremongering” after it used a party political broadcast on the BBC to warn of the dangers of Turkey joining the EU, highlighting its Muslim population and claiming 15 million of its citizens could migrate to the UK.

The advert provoked a backlash from pro-EU campaigners and MPs, as well as claims of Islamophobia from Twitter users, some of whom said they were planning to report the party to Ofcom.

The four-minute Ukip advertisement warned about the number of “Islamic imam schools” in Turkey, highlighted the shrinking number of Christians, and showed a succession of images of minarets and women wearing headscarves.

It also reeled off a list of statistics about women suffering physical violence and a quarter marrying before the age of 18 as apparent justifications for why the country should not be allowed to join the EU.

Facebook Twitter Pinterest Screengrab from Ukip ad. Photograph: Ukip

The advert claimed Turkey would be the largest member in the EU and expect to receive a third of its structural aid budget. It ended by saying its potential entry as a member state was just one of the “major risks to Britain coming down the tracks from the EU”.

“When the referendum comes, vote to leave,” it said in conclusion.

The footage was criticised by pro-EU campaigners including Tim Farron, the Lib Dem leader, who said: “Everyone is used to the poisonous rhetoric of Ukip, working to play one community off against another but this takes it to another level.

“Ukip is using a party political broadcast, that means that they have brought the BBC and C4 into this. The use of minarets [is] purely a coded nudge and a wink to their supporters. This is abhorrent to many liberally minded people.”

A spokesman for Britain Stronger in Europe said the party was “trying to tarnish an entire nation and its people and degrading debate in this country” which was “completely beyond the pale”.

“Whatever your view on whether Turkey should or will join the EU, this is a new low in baseless scaremongering from Ukip,” he said. “There is no prospect of Turkey joining the EU in the foreseeable future, so this is just a clear demonstration of how Ukip have no economic or fact-based arguments.”

Labour MP Richard Burden said it was “hard to describe just how much is wrong with its tone”, adding that it was “stomach-turning if this is a taste of what’s to come from them”.