Low-paid migrant workers are an immediate drain on the public purse, costing taxpayers more than £150,000 each by the time they hit state pension age, according to the Government’s tax and spending watchdog.

The Office for Budget Responsibility (OBR) said the average low-earner who came to Britain aged 25 cost the Government more overall than they paid in from the moment they arrived.

The cumulative bill rose to an estimated £151,000 by the time they could claim the state pension at 66, the watchdog said.

This is because low-paid migrants – who the OBR assumes earn half the average wage – put more demand on public services such as the NHS compared to their relatively low-tax payments.

The OBR estimated the cost to the public purse rose to almost £500,000 if they lived to 80, and more than £1m if they lived to 100.

By contrast, the average British-born worker boosts the public finances by £280,000 by the time they reach 66, even adjusting for education and health spending before they start work.

While low-paid migrants are a drain on public finances, the OBR found that the average migrant worker pays more in tax than they receive in public services throughout their lives compared to British-born workers. This is mainly because they are not educated in the UK.

Migrants also pay visa fees and health care charges, which the OBR estimates at around £12,500 for a migrant on a Skilled Worker visa who settles in the UK. Most migrants are also not eligible for welfare benefits for the first five years of their stay.