The CQC made the point that the independent health sector was important not just for privately funded patients or those with insurance but also many in the NHS because of contracts held with health service commissioners and trusts.

The report said these independent providers were developing their activities beyond doing routine surgery for NHS trusts. This includes work done within an overall patient journey through NHS care, for example providing scanning services for trusts.

In his letter to private providers, Mr Hunt said that hospitals who want to work with the NHS must "get their house in order and improve safety".

Private hospitals have been given two weeks to respond to the letter and set out what actions they will take.

How much of the NHS budget is spent in the private sector?

NHS spending with private sector providers in England was just over £9bn in the 2016-17 financial year - that's 7.7% of the Department of Health's revenue budget, a figure similar to the previous year.

That includes work done by private hospitals, such as hip and knee replacements, and contracts to run services such as community health and physiotherapy which were put out to tender by commissioning groups.

This proportion of overall spending has been growing steadily in recent years.

This partly reflects the government's health reforms in 2013 which obliged commissioners to consider non-NHS groups for contracts.

NHS spending on private provision began under Labour to bring down waiting lists.

According to NHS Partners network, which represents non-NHS health organisations, 24% of all gastroenterology, trauma and orthopaedic NHS patients are treated by independent providers (both private and not-for-profit).

The organisation says that 515,000 non-urgent operations and surgical procedures were carried out by private clinicians for the NHS in 2017, about 6% of the total.

Source: BBCNews