David Cameron has dismissed Labour claims that child benefit could be targeted to help shave £12 billion off the welfare bill, insisting there will be "no cuts" or changes to the handouts.

The Prime Minister defended Tory proposals to curb benefits spending, arguing that unlike Ed Miliband and Nick Clegg he did not think the existing system was "okay".

Finding savings was the only way to protect the NHS and other budgets, he said in an interview with ITV News.

But he added: "Let me be absolutely clear. We are not cutting child benefit, we are keeping child benefit.

"We have announced our plans which is to go on freezing child benefit for a couple more years. But it is an absolutely crucial benefit and with me as Prime Minister it stays."

Pressed on whether that meant there would be "no changes to higher rate, no means testing", Mr Cameron replied: "We had those proposals put to us, we rejected them. They are not right.

"We keep child benefit, we don't cut child benefit."

Challenged again on whether it would be kept "in the current form for the next five years" he said: "I said that last night, I am happy to say it again today."

Mr Cameron said: "If you want a balanced plan you need to reform welfare and get people back to work and reduce the welfare bill. Otherwise you will have to make excessively deep spending reductions in government departments.

"My opponents in this election - Ed Miliband and Nick Clegg - both think the welfare system is okay, don't reform it.

"I don't think it is okay. It's not okay that it still pays some people not to work.

"It is not okay that we have a system where young people can sign on and start a life on welfare. That is not okay."

Mr Cameron used a town hall style meeting at the Leeds offices of Asda this morning to reiterate his warnings about a Labour government supported by the SNP.

He insisted Mr Miliband's statement during last night's BBC Question Time Special that he would not enter coalition or do deals with the nationalists "changed nothing".

"What Ed Miliband said last night changes nothing," he said. "Is he really saying 'If Labour don't get a majority, but Labour and the Scottish National Party is a majority, I won't be prime minister'? Of course he is not saying that.

"So the threat today is the same as the threat yesterday - Ed Miliband propped up by the SNP, not governing on behalf of the whole of the country. That's the problem, and Labour shadow ministers have been out this morning confirming that my view is correct."

Mr Cameron denied he was trying to "de-legitimise" Scottish MPs with his warnings about the "chilling" threat of SNP influence.

Asked whether he was stoking up English nationalism for political purposes, the premier replied: "I am not. I am absolutely not.

"I am just pointing out the consequence of what the polls are saying, which is that the SNP win potentially every seat in Scotland - the consequences for that are a government of the UK of a weak Ed Miliband propped up by the SNP on a vote by vote basis, which would be very bad for the rest of the country.

"Because those SNP MPs - they have got a right to be there, but they do not want our country to be a success. They do not want our country to exist."