Video report by ITV News Political Correspondent Paul Brand
New NHS figures show the health service in England is performing at its worst ever level against key targets on A&E, cancer care and the wait for operations.
Some 4.42 million patients - the highest ever number - are on the waiting list for treatment, while one in six patients waits too long in A&E and there are longer waits for cancer care and operations such as hip replacements.
Health charities and think tanks have described the NHS as in crisis, with emergency care doctors saying the service is "imploding".
However, Health Secretary Matt Hancock said the NHS is in many ways performing better than ever, leading Labour to accuse the Tories of being "staggeringly out of touch".
Mr Hancock pointed to the rising number of patients requiring treatment and said the number of operations done had actually risen by 7% over the last 12 months.
"In many ways, the NHS is performing better than it ever has. The challenge is that demand is increasing as well," he told BBC Radio 4's The World At One programme.
"The performance of the system is incredible. The people who are working in the NHS are doing a remarkable job.
"We are putting record amounts of funding in over the next four years. We have got record numbers of doctors and nurses, with more to come."
But shadow health secretary Jonathan Ashworth said: "This is staggeringly out of touch.
"Matt Hancock is clueless about the levels of pain and misery he and his Tory cuts have caused patients.
"He insists 'in many ways the NHS is performing better than it ever has' on the day it's confirmed the NHS A&E performance is the worst ever.
"This shows the Tories simply don't care about our NHS."
Labour - which unveiled its NHS spending plans on Wednesday - seized on the figures to attack the Conservative government.
Leader Jeremy Corbyn said it is "disgraceful" that figures from NHS England show that A&E performance is at its worst-ever level.
In an interview, he said: "That's one in five of everyone accessing an A&E department hasn't been seen within the required four hours.
"The four-hour limit of seeing people was brought in under the previous Labour government, as was the two-week wait for cancer treatment. Neither of which are being met across the whole country.
"It is disgraceful and it is a problem of the lack of staff and the lack of funding for it."
And Liberal Democrat health spokesperson, Luciana Berger, said: "This is a damning indictment of the Conservatives' dismal record on the NHS."
She told ITV News that people would be "appalled" by the waiting times and that Brexit was not helping as EU workers were being dissuaded from joining the health service.
But Boris Johnson said only the Tories could be trusted to have a "strong, dynamic economy" to ensure the rises in the NHS budget being planned could be made.
The Prime Minister insisted he was "immensely proud" of what the NHS was achieving.
He said the £34 billion the Conservatives had pledged would go towards "20 hospital upgrades, 40 new hospitals - and, yes, it will help to deal with waiting times, in A&E, and at GP surgeries".
Mr Johnson had earlier told ITV News: "I believe people will see the change very quickly, but, what would be catastrophic would be to ask the NHS to run a four-day week - that's going to be absolutely chaotic for waiting times and GP surgeries."
He warned that a Labour government would "rack up such colossal debt" that it would be impossible to invest the necessary money into the health service.
The new NHS data shows that one in six patients waited longer than four hours in A&E in England during October - the worst ever performance since the four-hour target was introduced in 2004.
Some 83.6% of patients arriving at A&E were treated or admitted in four hours.
The target is 95% but it has not been met since July 2015.
The data also showed that in September, 84.8% of patients started treatment within 18 weeks against a target of 92%.
The target was last met in February 2016.
The target to start cancer treatment within 62 days of an urgent referral is also being missed.
Some 76.9% of cancer patients started treatment in 62 days in September, below the 85% target.
Overall, more than 4.4 million patients are on the waiting list.
The data comes as the Royal College of Surgeons called on political leaders to keep the 18-week wait for planned treatment - which is currently under review and could be scrapped.
Nuffield Trust chief economist Professor John Appleby said: "These figures show the next government will immediately be faced with one of the bleakest winters in the NHS's history."
Prof Appleby added: "We have many months to go until seasonal pressures really hit the NHS, but October has already seen an unprecedented slump, with performance against the main A&E target worse than ever.
"The health service is seeing far more patients, yet one in six is now waiting more than four hours in A&E.
"If the usual trends continue after Christmas, that would head towards one in five.
"Meanwhile, the number of people waiting on trolleys in corridors because no beds are available has already hit 80,000 - something we have only seen before in the very coldest part of the year.
"If this trend keeps going, I fear we could see 100,000 people stuck on trolleys this coming January.
"As the election promises roll in, we should be under no illusion about the money, staff and time it will take to turn this situation around."
Richard Murray, chief executive of the King's Fund, said: "Amidst the political rhetoric of the General Election campaign, today's statistics lay bare the stark reality for patients across the country who are struggling to access NHS hospital services."
An NHS spokesperson said: "These figures show that while NHS staff are looking after a markedly higher number of older and sicker patients, a higher number of patients are being seen quickly than a year ago."
In March, NHS England announced proposals to scrap the key targets for patients to be seen in A&E within four hours, or to receive an operation within 18 weeks.
Under new targets being piloted, those patients with the most serious conditions such as heart attacks, strokes and sepsis, would receive rapid treatment within an hour, while people with more minor conditions can expect to wait longer in A&E.
Data would be published on how long patients spend on average in A&E and the 18-week target would be replaced by an average marker of the time it takes to start treatment.