David Cameron has promised a "bare knuckle fight" with Prime Minister Gordon Brown as he launched a campaign to safeguard district hospitals.
The Tory leader is seeking to regain the political initiative amid reports Mr Brown could capitalise on his poll lead by calling an early election.
Mr Cameron has identified 29 hospitals he claims are under threat from cuts.
Labour accused Mr Cameron of making "misleading" promises on public spending and tax cuts.
Public health minister Dawn Primarolo said: "It's misleading or dishonest to, on Friday, for the Tory party to support £21bn worth of cuts from public services in supporting the Redwood commission proposals.
"And then come back and say suddenly not only are they not going to do that, they are going to invest in public services and we know that's not true."
The Conservatives last week pledged to consider tax cuts following a report by a policy group chaired by former Cabinet minister John Redwood.
The report prompted Labour accusations the Conservatives were "lurching to the right" - something denied by Mr Cameron, who has pledged to fight on the centre ground.
Mr Cameron said the downgrading of services at district hospitals would be a key battleground at the next general election.
"I can promise what I've called a bare-knuckle fight with the government over the future of district general hospitals.
"We believe in them, we want to save them and we want them enhanced, and we will fight the government all the way."
He launched his campaign on Monday with a visit to Worthing Hospital in West Sussex which faces the possible closure of its A&E, consultant-led midwifery and intensive care units.
He continued with a visit to Sandwell General Hospital, West Bromwich and Huddersfield Royal Infirmary on Tuesday.
Mr Cameron called for an immediate moratorium, stopping cutbacks at district general hospitals and putting in place a system making it more likely that they can survive.
He said: "What that means is scrapping a lot of the top-down health targets that the government has introduced, it means ending the pointless reorganisations, of which we have had nine over the last decade, and it means reviewing the costly and wasteful NHS computer.
"Then it means actually making sure that hospitals can work together and GPs are put in the driving seat in terms of commissioning care to their patients."
The government has said there are 13 NHS trusts where services are the subject of a review or consultation - which may include more than one hospital each.
"The NHS is looking at the safest and most effective way of delivering care," said a department of health spokesman.
"This does not mean wholesale closures of district general hospitals but it does mean that NHS clinicians and managers need to work with local communities to decide on the best organisation of services for patients in their areas."
The Conservative campaign comes as the Emergency Medicine Journal published research suggesting the closure of local A&E departments will put the lives of seriously ill patients at risk by making them travel further for treatment.
However, the government said the study of 10,000 cases in four ambulance services between 1997 and 2001 was outdated and did not take into account developments in ambulance care.
Mr Cameron is also concentrating on the fight against crime.
He told Today that if people broke the law they should expect "tough penalties" but that punishment was "not enough".
"We are not going to deal with anarchy in the UK unless you actually strengthen families and communities in the UK."
He suggested one way to do this was to have a tax and benefit system that encouraged families "to come together and stay together rather than driving people apart".
Mr Cameron hit back at claims he had "underestimated" Gordon Brown, in an interview with BBC Radio 4's Today programme.
"He's been chancellor for 10 years, he managed to dislodge the prime minister who had won three elections. I've never underestimated Gordon Brown."
But he said in the run-up to the next general election people would see all of the problems facing Britain - from NHS closures to social breakdown - can be traced back to Mr Brown "sitting at his desk in Number 11 Downing St as chancellor".