Shabana Mahmood will announce sweeping new rules on Monday on how long legal migrants must wait for settlement in the UK, with most likely to wait a decade and some up to 15 years.

Ministers – including the housing secretary, Angela Rayner – had raised concerns about the effect the rules would have on care workers already in the UK who would be likely to face a 15-year wait for settlement, also known as indefinite leave to remain (ILR).

The government’s response to the consultation on the reforms, which will be put before MPs on Monday, is expected give some exemption to care workers already in the UK, though most other professions will face the lengthy waits for settlement.

Mahmood, the home secretary, has proposed that the settlement wait could be reduced if legal migrants showed they had contributed to their local communities via a “points based system” or if they were earning higher incomes.

She is expected to meet union general secretaries on Monday – some of whom have raised alarm at the changes – to map out the final details.

The Guardian first reported in July that the prime minister, Andy Burnham, was considering exempting hundreds of thousands of care workers from the reforms to relieve pressure on the social care sector. The Home Office has granted about 200,000 health and care worker visas in the last five years, with many more people coming as their dependants.

Under the plans published for consultation, the standard qualifying period for settlement would double from five to 10 years, while some workers in occupations below graduate level, including care workers, could face a 15-year qualifying period, subject to proposed exemptions and reductions.

In June, Rayner described making care workers already in Britain wait up to 15 years for permanent residence as “un-British”. In September, the energy secretary, Miatta Fahnbulleh, said the plans would have been “tough” for her family, who came to Britain as refugees.

In a letter to Mahmood and the health secretary, Yvette Cooper, seen by the Guardian, parliamentarians and organisations representing migrant workers, racial equality campaigners and health professionals describe the proposals as “an iteration of Windrush era policies”.

The Windrush scandal, exposed by Guardian reporting in 2017, involved mainly Black Britons being wrongly detained, deported and denied access to work and essential services, despite having the right to live in Britain.

In their letter, dated 29 October, the signatories urge ministers to “stop history from repeating itself” by abandoning the proposals or, at a minimum, introducing extra safeguards.

Signatories argue that changing the rules for people who have planned their lives around existing settlement requirements would be unfair and could encourage essential workers to leave the country.

They warn that proposed exemptions for some public-service workers may fail to protect staff employed by independent health and social care providers, as well as workers’ family members.

The letter urges ministers to follow the recommendations of the Windrush Lessons Learned Review, conducted by Wendy Williams, which called for improvements in the development and scrutiny of immigration policy, including greater consideration of its impact on affected communities.

The Labour MPs Bell Ribeiro-Addy, Diane Abbott, Clive Lewis and Rachael Maskell are among the signatories, alongside the Green MPs Ellie Chowns, Carla Denyer, Siân Berry and Hannah Spencer. Organisations backing the letter include the Work Rights Centre, Action for Race Equality, Care England and the Society of Radiographers.

The signatories write: “Windrush was a scandal borne from racist immigration policies … this situation is not historic when this same wrong persists, and the same groups are targeted by current immigration proposals.”

The signatories warn the health and care sector is already “dangerously under-staffed” and that the proposed changes risk “worsening the health and wellbeing of everyone in the UK”.

The letter argues that the government could struggle to meet cancer treatment and NHS waiting-list reduction targets without retaining and expanding the workforce, particularly in professions heavily reliant on internationally trained staff, like radiography.

It raises particular concerns about adult social care, adding: “International workers are essential to maintaining current levels of care. Without them, services will contract, and unmet need will increase.”

Launching the consultation on earned settlement last year, Mahmood described Britain as a “multi-faith, multi-ethnic democracy” that demanded “contribution and integration”. She added: “To become a part of this country, permanently, is therefore not a right but a privilege – and one that must be earned.”