Privatisation of NHS care will be significantly curbed under confidential plans that health service bosses expect Downing Street to include in the Queen’s speech next month.

Local NHS bodies in England would no longer have to put out to tender any contract worth at least £615,278. That requirement has contributed to a big increase in outsourcing of services and a record £9.2bn of the NHS’s budget now being handed to private firms.

Under NHS England’s proposals, Boris Johnson would have to scrap key elements of Andrew Lansley’s shake-up of the NHS in England in 2012, which bitterly divided the then coalition government.

The Guardian has obtained an NHS England document which summarises 22 key changes it believes will be included in an NHS reform bill due to be published next month.

A twin-pronged attempt to severely restrict future privatisation would involve scrapping section 75 of the Health and Social Care Act 2012 and removing the commissioning of healthcare services from the remit of the Public Contracts Regulations 2015.

The proposals also seek to limit the role of competition between different parts of the NHS, which critics claim has proved costly, damaging and a distraction from caring for patients.

The proposals are likely to gain government backing because NHS England was asked to draw them up by Theresa May when she was prime minister, in order to allow changes in how the health service operates to go ahead as part of its ambition under the long-term plan to integrate care.

“This is long overdue. These proposals would protect the NHS from the worst excesses of privatisation and end the situation where different parts of the health service have had to compete against each other,” said Sara Gorton, the head of health at the union Unison.

“Our precious NHS needs to be in the best possible state so it’s protected when the UK leaves the EU, whether it’s with or without a deal. It must be able to fend off the circling vultures who would see it torn up in pursuit of profit.”

Section 75 of the 2012 act led to NHS clinical commissioning groups (CCGs) tendering thousands of mainly small-value contracts, 40% of which were won by private firms. That led to an increased fragmentation of NHS care, with profit-driven companies taking over key types of diagnostic and treatment services.

The plans are likely to become public at NHS England’s board meeting on Thursday.

Dr Tony O’Sullivan, the co-chair of Keep Our NHS Public and a retired paediatrician, backed the repeal of section 75. “Some of the most controversial clauses have led to the carve-up of the NHS into contracts and a competitive market.”

But the bill should go further and outlaw all privatisation of any clinical services and reinstate the NHS as the sole provider of its own array of services, he added.

NHS England’s controversial attempt to take PET-CT cancer scanning services in the Thames Valley away from the Oxford University Hospitals NHS trust and hand them to the firm InHealth showed that it could not be trusted, he suggested. The plan caused an outcry and NHS England was forced to back down.

In a break with normal procedure NHS England officials, led by its national director of strategy Ian Dodge, have drafted the bill, rather than the Department of Health and Social Care.

It will also include proposals to:

• Allow the creation of a new type of NHS trust, called “integrated care providers”.

• Let NHS England and NHS Improvement, the service’s financial regulator, extend their already close working relationship into a full, legal merger.

• End the Competition and Markets Authority’s role in the NHS, which could lead to more NHS trusts merging.

The cross-party Commons health and social care select committee has already given its backing to NHS England’s proposed legislative changes.