Labour has attacked the government's decision to reinstate VAT on personal protective equipment (PPE) such as face masks as "unbelievable".
The party says reintroducing the tax - which was suspended in May - could cost families nearly £100 over six months.
Face masks are mandatory in places such as shops to slow the spread of Covid.
The government said: "The VAT relief was designed to accelerate supply of PPE to the health and social care sectors... when they needed it most."
And a spokesperson said the government had committed to provide free PPE for Covid-19 needs to adult social care until March 2021.
The tax relief was initially introduced in May at a time when demand for PPE outstripped supply.
The government has said it has been buying up more PPE and boosting domestic manufacturing in order to avoid shortages in the future, and outlined how health and social care services can access free PPE through its Winter Plan.
VAT was due to be reintroduced in August, but in July the suspension was extended until 31 October. The six month period is estimated to have cost the government £255m.
As well as face masks, PPE also includes gloves and aprons.
The VAT cut applied specifically to medical grade PPE, which includes fluid-resistant surgical masks but not general face coverings.
Labour has calculated that for a family of four using disposable masks (two adults and two teenagers) the reintroduction of VAT could cost an extra £94 over the next six months.
Shadow financial secretary to the Treasury, James Murray, said: "It's unbelievable that the government wants to introduce a mask tax in the middle of a pandemic.
"With Covid cases on the rise across the country, the government should be doing all it can to help people follow its own guidance to wear a mask, not ramping up the cost of buying one."
VAT or value added tax is the tax you have to pay when you buy goods or services. The standard rate of VAT in the UK is 20% and in 2019-20 it is expected to raise around £136.6bn for the government.