Registered UK charities and non-profit organisations will be able to support community groups welcoming refugees to Britain under new Labour measures, with arrivals initially expected to number in the hundreds next autumn.

Shabana Mahmood, the Home Secretary, has introduced the arrangements to provide safe and legal migration routes. The Home Office says numbers will be capped according to “community capacity to sponsor refugees”, before growing into the low thousands.

Sponsors will help establish and support local groups and verify sponsorship arrangements. The stated limit therefore links the scale of admissions to communities’ ability to support arrivals, rather than setting an unrestricted route.

Chris Philp, the shadow home secretary, argued that the scheme would create “yet another hole” in Britain’s borders. He said: “The Government is effectively surrendering control of our borders to anyone that can set up a charity. Some of these charities are likely to have links to extremists.” His allegation of extremist links was not accompanied by supporting evidence.

The measures come as Mahmood prepares to unveil settlement reforms next week, amid speculation that she will soften proposals to increase the qualifying period for indefinite leave to remain from five to 15 years.

More than 100 Labour MPs oppose the reforms. Cabinet critics, including Angela Rayner, the Housing Secretary, and Miatta Fahnbulleh, the Energy Secretary, argue that applying the rules retrospectively would be unfair to migrants already working in Britain.

Andy Burnham has publicly supported the principle of reform, but on Monday refused to endorse a 15-year eligibility period. He is privately understood to favour an exemption for care workers. A faster settlement route for foreign care workers is among the options under consideration; no decision is reported.

Mahmood’s initial proposals, set out a year ago, allowed a five-year reduction for migrants who had worked in a specified public service occupation for five years. Higher-rate taxpayers earning more than £50,270 would also receive a five-year reduction, while additional-rate taxpayers earning above £125,140 would receive seven years off, in a proposed reward for skilled workers.

The Home Office is understood to be examining whether professional history and commitment to a particular sector could shorten the wait, potentially accommodating care workers. The Prime Minister has separately pledged a social care system for elderly people that is free at the point of use.

At Labour’s Liverpool conference last month, Mahmood indicated that a compromise would be “fair” to tens of thousands of migrants already in Britain. How far any concessions will protect existing workers, and whether care workers will receive a distinct exemption, remain unresolved.