David Cameron has mounted a personal attack on Ed Miliband as he accused the Labour leader of presiding over a group of “hypocritical holier-than-thou, hopeless, sneering socialists” who have betrayed their traditional values.

Speaking at the Conservative spring conference in Manchester on Saturday, the Tory leader admitted the upcoming general election was “on a knife edge” but said that with five years’ experience he believed he was the right person to lead the country rather than Miliband.

The prime minister said that “this is a high-stakes, high-risk election” and claimed it was a contest between just two parties: Labour and the Conservatives.

He also accused Labour of betraying its traditional values and no longer representing working people.

As he delivered his speech, the first rallying call since MPs left Westminster to start the election campaign Cameron defended his personal attack on the Labour leader.

He said: “Some might say: ‘Don’t make this personal’, but when it comes to who’s prime minister, the personal is national.

“The guy who forgot to mention the deficit could be the one in charge of our whole economy.

“The man who is too weak to stand up to the trade unions at home could be the one facing down our enemies abroad.

“The leader who thinks leadership is climbing aboard the latest bandwagon – he could be the one taking the make-or-break calls in the middle of the night.”

He has previously accused the Labour leader of planning to “crawl up Downing Street on the coat-tails of the SNP”.

Cameron also explained his plans to make the NHS a priority by offering a full seven-day service, with senior doctors available to treat patients at weekends in a bid to reduce mortality levels.

At the moment, patients are more likely to die on a Saturday or Sunday, with inexperienced junior doctors frequently left to cover hospitals at weekends, when some specialist services are not available.

He said: “And the truth is that you are actually more likely to die if you turn up at the hospital at the weekend. Some of the resources are not up and running. The key decision-makers aren’t always there.

“With a future Conservative government, we would have a truly seven-day NHS.

“Already millions more people can see a GP seven days a week, but by 2020 I want this for everyone, with hospitals properly staffed, especially for urgent and emergency care, so that everyone will have access to the NHS services they need seven days a week by 2020 – the first country in the world to make this happen.”

But Cameron’s decision to announce his seven-day care plans as the campaign trail begins has provoked the criticism that he is misleading voters and partaking in “shameless political game-playing” as polling day nears.

Lucy Powell, Labour’s vice chair, said the Conservatives’ spending plans would mean extreme cuts to the NHS.

“On the NHS, David Cameron misled people in 2010 and he’s misleading them again today,” she said.

“When he pledges seven-day-a-week care in the NHS, people will remember that he did exactly the same before the last election, only to break his word. After five years of the Tories it’s harder to see your GP and A&Es are in crisis.”

Labour ministers, as well as the British Medical Association council, have questioned where the money to deliver extra weekend care will come from.

Dr Mark Porter, who chairs the British Medical Association council, said: “Without a detailed, fully costed plan to provide the staff and resources needed to deliver more seven-day services, this is at best an empty pledge and at worst shameless political game-playing with the NHS ahead of the election.”