Brexit campaigners' promise of a points-based immigration system would be met with a tit-for-tat response from other European countries, the Dutch prime minister has warned.
Mark Rutte said Boris Johnson and Michael Gove's plan to stop the free movement of EU citizens into Britain and introduce a skills-based immigration system would result in a "race to the bottom".
He said other European countries would react by making it harder for Britons to go and live and work in the continent.
The Leave camp's Australian-inspired idea would end the automatic right of EU citizens to come to live and work in the UK, and instead migrants would only be allowed in if they fill certain skills criteria.
Mr Rutte said the Netherlands would have to adopt a similar approach if it was introduced in the UK.
He told BBC News: "It would be unavoidable, inevitable for us and I think for many of us in Europe to follow the same proposals to implement a points system also in the rest of the European Union.
"So you would get a race to the bottom and that's exactly what you don't want."
Treasury chief secretary Greg Hands welcomed Mr Rutte's intervention, tweeting: "Leave's 'immigration points system' already unraveling (sic) as Dutch PM Mark Rutte makes clear".
Chancellor George Osborne branded the plan "fantasy politics" and said it would lead to more immigration.
On a visit to a logistics firm in Harlow, Essex, the Chancellor said: "What a contrast today between the Leave campaign with their fantasy politics - unworkable proposals that will increase immigration, take us out of the single market and cost us jobs - and the reality check in the real world of the highly respected OECD which points out the grim economic future for the UK outside the EU."
Remain campaigners have said Australia has double the number of immigrants per head than Britain and highlighted experts' claims that the plan would not have the desired effect.
But the Leave camp is confident it has the upper hand with voters who are concerned about immigration and can persuade them to back Brexit.
Ukip leader Nigel Farage said a points-based system would allow Britain to set a cap on the number of people coming into the country.
On a visit to Leeds, he said: "The point about an Australian-style system is that you chose. You set your number.
"I know more about this than most people. Every single year, Australia looks at what it thinks it needs to expand its country. It's growing its country so it takes more people pro-rata than we would.
"But the point about it is that we can choose."
Mr Gove, Mr Johnson, alongside Tory minister Priti Patel and Labour Brexiteer Gisela Stuart, promised to create a "genuine Australian-style points-based immigration system" by the 2020 general election if voters back Brexit.
It would end the automatic right of EU citizens to live and work in the UK, with immigration instead based on skills and qualifications without discrimination on grounds of nationality.
Mr Gove dismissed suggestions that Mr Rutte was criticising the points-based plan.
He told the BBC: "I don't think that the Dutch prime minister was saying anything other than this is an enviable scheme which will have other countries thinking that Britain is doing the right thing for its citizens and its economy."
Home Secretary Theresa May admitted the present level of immigration is too high but argued leaving the EU and damaging the economy is not the solution.
The pro-EU campaigner said: "If you look at the figures, Australia has nearly double the level of immigration per head that we have here in the UK.
"Now the current level of immigration is too high, but there is no silver bullet; controlling immigration is hard.
"What it requires is a concerted effort across a range of fronts and we have shown that where we take action, we can bring the numbers down but there is more to do."
