Senior Tories have called on David Cameron to increase NHS spending significantly as a former coalition health minister forecasts a collapse in the service.

A slew of bad news over the NHS has raised Tory fears that the health service could again prove to be a toxic issue just 10 months before a general election.

The NHS says 299,031 patients arrived at A&E departments last week – the highest number on record. A&E waiting time targets were missed for the 49th consecutive week and a record number of beds were filled last month by patients who could not be discharged, often because community or social care services were not in place.

Stephen Dorrell, a former Conservative health secretary, Sarah Wollaston, a Tory MP, and Paul Burstow, a former coalition health minister, say that with the economy growing the NHS must receive a real terms increase in spending over the next five years if it is to function properly.

For the past four years, the government has ringfenced the health service budget from cuts and raised funding in line with inflation, but largely relied on efficiency savings to pay for a growing demand for its services.

Dorrell and Wollaston, elected this month as chair of the Commons health committee, replacing Dorrell, said the policy could not continue. Paul Burstow, a Liberal Democrat health minister in the first two years of the coalition government, said he believed the NHS needed an extra £15bn from the Treasury over the next five years "if you don't want the system to collapse during the course of the next parliament".

The grim analysis is backed by some of the country's top health experts. Writing in this newspaper, professor Chris Ham, chief executive of the health thinktank, the King's Fund, and a former Downing Street adviser, raises the spectre of another major NHS disaster on the scale of the Mid Staffordshire scandal if more money is not found to relieve the pressures on services.

He says the danger is that "the quality of patient care will be compromised by not having enough doctors and nurses on the wards and in surgeries and clinics. The well-publicised failures of care at Mid Staffordshire NHS Foundation were caused by precisely this kind of cost cutting, with tragic consequences for the families concerned."

Cameron has previously been advised by the former defence secretary Liam Fox and other senior colleagues to commit to removing the ringfencing of the NHS budget after 2015, leaving it open to cuts in the next parliament. Many Tory MPs believe that, at 10% of GDP, spending on the NHS has reached its limit.

Dorrell, who claimed that the challenge to make £30bn efficiency savings to redistribute around the NHS had failed, said he would be ashamed if the NHS budget did not receive a boost in income at a time when the economy was growing. "I am in favour of the government not denying what 5,000 years of history tells us is true, which is that every time a society gets richer it spends a rising share of its income on looking after the sick and the vulnerable," he said.

Wollaston, a GP for 20 years before becoming an MP in 2010, said: "If there is not an increase, it is hard to see how we could maintain current levels of service given the rising demand.

"The NHS budget has been protected in line with background inflation but that does not keep pace with inflation in health costs from rising demand and demographic changes. I don't want to see any reduction in services; I would like to see further improvements and that will require an increase in funding."

The NHS is looking likely to be a key battleground at the general election and Labour will seek to keep it at the forefront of the public mind in the coming months. This week it will use a private member's bill to lay out how it would repeal the coalition government's controversial health and social care act, which ushered in greater private sector involvement in the NHS.

The bill, proposed by Clive Efford MP, would rewrite the rules that force market tendering of services. It will be debated in the Commons in November and Labour candidates in marginal seats will call on Tory and Lib Dem incumbents to back the bill, while highlighting examples of how current rules waste money and fragment care.

Shadow health secretary Andy Burnham claimed the vote on the bill would "without doubt be the defining moment of what remains of this parliament". He added: "Cameron's biggest mistake by far is his decision to break the coalition agreement promise of 'no top-down reorganisation of the NHS'."