David Cameron has defended government plans to begin charging migrants treated in accident and emergency departments, insisting the proposals were enforceable.
The Prime Minister said it was right to charge foreign visitors for using the NHS, as he insisted that future migrants to Britain would face more stringent rules before being able to move here.
He said of the proposals: “We should do it.”
Speaking to the BBC's Andrew Marr Show, he said the plans were workable: “Yes we can, we can.
“Our NHS is a national treasure and we can all be incredibly proud of it, and it is right that we all pay into it and everyone here has access to it for free.
“But people who come to our country, who don't have the right to use it, should be charged for it and we're putting that in place.”
Mr Cameron would not be drawn on how many people he expected to come to Britain after immigration restrictions were lifted for Romanians and Bulgarians on January 1, saying he wanted to avoid repeating the “ludicrous” mistakes made by the previous Labour government.
He said: “We're not making a forecast because I think it's unlikely we'll get that forecast right.
“The last forecast that was made by the last Labour government, at the time of Poland's accession to the EU, where they put in no transitional controls, was a ludicrous forecast of 14,000 and it turned out that over a million people came.”
Mr Cameron said that by ensuring the minimum wage was being paid to all employees and clamping down on illegal immigrants, the Government was getting a grip on immigration.
He added that his administration would “make sure that people who can't sustain themselves are removed from our country”.
The Prime Minister said of reports that some UK-based migrants are claiming child benefit for the children they have left behind in their home country: “Well, I don't think that is right and that is something I want to change.
“It's a situation that I inherited. I think you can change it, I think it will take time because we either have to change it by getting agreement with other European countries, and there are European countries who, like me, think it's wrong that someone from Poland who comes here and works hard - and I'm absolutely all in favour of that - but I don't think we should be paying child benefit to their family back at home.”
He said one way of changing that was “the treaty change that I'll be putting in place before the referendum that we'll hold on Britain's membership of the EU by the end of 2017”.
Asked if immigration had been positive or negative for Britain, he replied: “Well, it's been too high. I'm in favour of managed migration.”
Mr Cameron insisted that Britain would be able to dictate the terms of any future agreements with Brussels.
He said “that is absolutely achievable”.
“So Britain will be able to insist, for future countries joining, we'll be able to insist on a tougher, more robust regime.”
But he admitted that he had not yet been able to deliver his 2010 pledge to reduce net migration down to the tens of thousands.
“Well, it's down almost a third since I became Prime Minister, so I said we wanted to get net migration down, I said we wanted to get it to the tens of thousands, we are not there yet, but it has come down by just less than a third.”
Mr Salmond described Mr Cameron's position on a TV debate as "increasingly ridiculous", and insisted that the Prime Minister will be "dragged into the television studio" eventually.
"David Cameron's attitude is the same mix of arrogance and fear that saw the Tories seek invisible cuts to Scotland's budget in the 1980s and plan £4 billion of cuts for the future," he said.
"Arrogance because his government wants to dictate the terms of the debate but refuses to take part in a public debate and fear because he knows, as people across Scotland do, that he represents a government Scotland did not elect.
"The Prime Minister's position is increasingly ridiculous. He cannot on the one hand tell the BBC that the referendum debate will take place in the media and then simply refuse to debate.
"A majority of people, not just in Scotland but in the rest of the UK, think it is right that the Prime Minister takes part in a debate and I would suggest David Cameron listens to them.
"He can only hide from this for so long. Eventually he is going to be dragged into the television studio and have the democratic responsibility of an open, free debate."
A Better Together spokesman said: "You've got to hand it to Alex Salmond.
"On one hand, he and his ministers are desperately trying to shut down any debate in Scotland, while at the same time they are crying foul because they aren't getting to choose who speaks for their opposition.
"David Cameron doesn't have a vote. Alistair Darling does. If Salmond wants a debate, we are ready to have one."