EU citizens have been able to "treat the UK as though it's part of their own country" for too long, British prime minister Boris Johnson said on Sunday, sparking widespread criticism.

"I’ve said that what we want to do is bear down on migration, particularly of unskilled workers who have no job to come to and I think that’s what’s happened over the last couple of decades or more," Johnson told Sky News.

"You’ve seen quite a large number of people coming in from the whole of the EU — 580 million population — able to treat the UK as though it’s basically part of their own country and the problem with that is there has been no control at all and I don’t think that is democratically accountable."

"You have got to have a system by which politicians can say to people, 'Well, yes, we are letting people in, but we are doing it in a way that is controlled and checked'."

The Conservative leader added that if his party won the election, he would introduce an "Australian-style" points-based immigration system after Brexit, which would effectively reduce low-skilled immigration to the UK.

Read more: Brexit: Are Boris Johnson's Tories being fair to future EU migrants?

The remark has created outrage, four days before a general election in which the PM hopes to win a parliamentary majority.

Johnson's strong words on immigration, in the last days of the campaign, may be intended to appeal to Eurosceptic voters in key constituencies.

"EU citizens are our friends, neighbours and colleagues - they contribute to our country and should treat it as their home", London mayor Sadiq Khan said.

The3million, a support group campaigning for the post-Brexit rights of the 3.7 million EU nationals living in the UK, described Johnson's comment as a "xenophobic rant" and said they were "outraged".

"To all candidates in the General Election, we say this is our home and you must work towards social cohesion and unity", the group said in a newsletter.

The group launched a petition asking for the British PM to apologise.

"It started with calling me and my fellow EU citizens in the UK 'citizens of nowhere' and 'queue jumpers'", the3million's petition read. At time of publication, over 1,600 people had signed the petition in a few hours.

"Just a few weeks ago, Mr Johnson praised our contribution and called us his 'friends, family and neighbours', but the tone has changed again."

European citizens took to social media to share their dismay at the PM's comment.

"It's too late, the damage has been done", one tweeted.

Read more:

What the Brexit deal means for EU citizens living in the UK

Britons living in EU countries 'denied democracy' in UK 'Brexit election'

Brexit Guide: Where are we now – and how did we get here?