The NHS should not be “complacent” about funding and would need to demonstrate it is “spending money well” under a Labour government, the shadow health secretary has said.

Wes Streeting said he will stress to the Treasury that investment in health and social care would boost the economy and focusing on prevention could save “thousands, if not hundreds of thousands” of pounds.

Speaking at an event hosted by the Institute for Government, he warned NHS leaders that the public feels anxious about the health service and could be receptive to “siren voices on the right”.

He said: “What I would say to the NHS is that we should not be complacent about the fact that healthcare spending now accounts for a huge proportion of departmental expenditure, a significant proportion of the country’s GDP.

“And I think the public feel a sense of real jeopardy and anxiety about the future of the NHS, and there are siren voices on the right that have always been there who say this system is simply not sustainable and shouldn’t we look at an insurance-based model or shouldn’t we look at people paying for certain types of healthcare in addition to the ones they already pay for.

“I don’t think we should be complacent about that.”

He added: “As well as making the case to the Treasury for greater investment in health and social care, the thing I would say to the NHS and social care leaders is you can’t be complacent about demonstrating that you are spending that money well, and I won’t be able to be complacent about demonstrating that we’re spending that money well if I’m the secretary of state for health and social care.”

Mr Streeting’s comments came as Health Secretary Sajid Javid described the NHS as a “Blockbuster healthcare system in the age of Netflix” and said it needs “big and bold changes”.

But while the Labour frontbencher acknowledged there needs to be some reform, he shied away from committing to major structural changes to the health service.

He said: “What I don’t want to do is say to a system that’s already burned out, exhausted and dealing with the worst crisis in its history, and pulling its hair out at competing, lopsided, misguided Government reforms (is) ‘Don’t worry everyone, what I’ve got up my sleeve is a new top-down reform agenda that I haven’t even discussed with you yet’.”

He also declined to commit to an inflation-linked pay rise for all NHS and social care staff, but said the Government should concentrate on boosting wages for the lowest paid in the sector.

Asked about the involvement of private companies in the NHS, Mr Streeting said he would use “whatever means necessary” to ensure people got the treatment they needed.

He said it is “morally unacceptable” that the country has a “two-tier” system with more people choosing to go private, but added that he would use the private sector to help clear the backlog.

He said: “I don’t think the British people would buy an ideological argument that said ‘because of our ideological principles we think you should be waiting longer’ and, secondly, I do not think a situation where working-class people who can’t afford to pay private wait longer is a left-wing position.”