Unions representing gig workers have attacked “paltry” offers of sick pay for delivery couriers affected by coronavirus that could push them to keep working to stay financially afloat rather than self-isolate.

DPD, whose 5,000 couriers deliver parcels for brands including Marks & Spencer and John Lewis, is offering self-employed couriers who need to self-isolate the equivalent of statutory sick pay (£94.25 a week). It is well short of the approximately £550 its drivers with worker status are supposed to earn weekly. DPD has also said costs of renting equipment and vans will not be waived but deferred.

Hermes, which has around 15,000 self-employed parcel couriers, will only pay £20 a day to drivers if they need to self-isolate and only if they typically earn less than £90 a day. It means that almost half its workers will receive nothing and those who do will see payments capped at £280 because they are effectively limited to 14 days.

Deliveroo, the takeaway delivery firm, says it will offer its 35,000 riders in excess of statutory sick pay (SSP), for up to two weeks of self-isolation if they have certifiably contracted the virus, or have verifiably been told to isolate themselves by a medical authority. But it did not specify how much higher the payments would be.

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In a statement that did not single out particular firms, the GMB trade union said it was irresponsible that companies which use the gig economy model “put courier safety and public health at risk by creating disincentives to self-isolation”.

There are more than 1 million gig workers in Britain who typically have no rights to SSP and are only paid per job because they are treated as self-employed contractors. Couriers are expected to be in high demand during the coming weeks as more people self-isolate and rely on deliveries of essentials.

“Paltry statutory sick pay for those who have to self-isolate is a financial punishment simply for doing the right thing, flies in the face of advice to employers, and exposes people to harm and hardship,” said Mick Rix, national officer at GMB.

“Ministers can and should use the emergency powers already available to them to ensure employers are no longer able to act in bad faith and place a requirement on them to support their people through self-isolation.”

DPD Group UK made £118m in profit in 2018 and Hermes made £29m over a similar period. Deliveroo almost doubled its turnover to £476m in 2018 but made a loss of £232m.

A spokesperson for DPD said the company “is taking steps to protect all its drivers, including those who choose to be self-employed”.

“In the event of a self-employed driver being impacted by coronavirus and needing to self-isolate, DPD will pay the equivalent of statutory sick pay from day one and their main operational costs will be deferred.”

Hermes said that it had moved quickly with its £1m support fund. “We believe that we are the first major company in the UK to establish a fund of this kind for its self-employed service providers,” a spokesperson said.

The company said it is targeting funds at its lowest earners “who may be more likely to require financial support”, adding: “We recognise that by agreeing to self-isolate themselves in accordance with government requirements, those couriers are benefiting their wider community while potentially suffering a negative financial impact themselves.”

A Deliveroo spokesperson said: “Riders’ safety is a priority and we want to make sure those who are impacted by this unprecedented virus and cannot work are supported. We’ll be with them every step of the way to provide support where we can during this worrying period.”

The ride-hailing app Uber has taken a different approach. It said it will pay drivers based on their average earnings for 14 days if they need to go off sick.

Andrew Macdonald, senior vice-president at Uber, said: “We continue to be concerned by the ongoing spread of coronavirus. We are supporting drivers and couriers who are diagnosed with Covid-19 or placed in quarantine by a public health authority. Drivers and couriers in these situations will receive compensation for a period of up to 14 days. This has already begun in some markets and we are working to implement mechanisms to do this worldwide. We believe this is the right thing to do.”

• This article was amended on 18 March 2020. An earlier version said Deliveroo riders who chose to self-isolate following medical advice were among those who would be offered more than statutory sick pay (SSP) for up to two weeks. This was due to an error in the information supplied by the company, and should have referred to riders who have verifiably been told to isolate themselves by a medical authority. This has been corrected.