Two leading retailers have criticised Stormont for failing to pass on the same relief schemes received by their counterparts in other areas of the UK.
They fear it could end many retail chains here.
Pete Boyle, director of Denvir Holdings, the company behind jewellery chain Argento, said he and his peers were "annoyed" at the imbalance, which he believes sees his firm suffer a shortfall of almost £1m.
He believes he would receive that figure in relief should his company be based in England.
Meanwhile, Stephen McCammon, managing director of fashion retail chain Menarys, said the Assembly was "butchering" Westminster's good intentions to mitigate damage done by Covid-19.
He believes his business will receive up to 78% less support than similar businesses in England, Scotland and Wales.
In the official guide for grant funding schemes for English medium-sized retail and hospitality businesses, it states: "Under the Retail, Hospitality and Leisure Grant (RHLG) eligible businesses in England in receipt of the Expanded Retail Discount (which covers retail, hospitality and leisure) with a rateable value of less than £51,000 will be eligible for a cash grant of £10,000 or £25,000 per property/businesses in England."
But Mr Boyle, who has 26 Argento stores here, believes he will receive just £25,000 for all of his stores from the Department for the Economy (DfE). He said: "Now we have to spread that £25,000 across all 26 shops, which is under £1,000 per store.
"We paid £10m in tax last year and the money we should be receiving for each of our stores would be used to cover rents and other bills while we are not operating.
"It's not a bonus for us, this is for our survival and we want to know who decided at Stormont that it would be done differently here and why."
Mr McCammon, who owns 18 Menarys stores, added: "Of our 18 towns in Northern Ireland, 10 shops would qualify for the RHLG but it seems the awarding of grants is to be limited to one per business.
"The Chancellor was robust in his 'headlines' and through the 12-month business rates holiday and the Retail, Hospitality and Leisure Grant it initially appeared that every opportunity was being given to our sector to ride out the Covid-19 crisis. However, the Assembly has interpreted this very differently and businesses like ours now have to rely entirely on debt through the CBIL to fund our businesses as we continue in lockdown."
A spokesperson at the Department for the Economy, which is managing the scheme, said: "The Executive agreed the £25k Business Grant Scheme on April 10. Part of the eligibility for this scheme is that businesses with multiple premises with a Net Annual Value (NAV) of between £15,001 and £51,000, and which meet all eligibility criteria, will be eligible for one grant of £25,000 in total."
It did not comment any further on why multi-premise retailers would only be awarded one grant as opposed to one per store.
Registration will open on Monday for businesses here to apply for the £25,000 Hospitality, Tourism and Retail Grant.