A CO Antrim-based company linked to the Owen Paterson controversy has declined to comment on calls for an investigation into how it was awarded contracts for Covid testing.
Labour leader Sir Keir Starmer said Prime Minister Boris Johnson should "commit to a full and transparent investigation into Randox and the government contracts".
His comments came during an emergency Westminster debate on standards rules and how the case of former Secretary of State Owen Paterson was handled.
Mr Paterson was found to have breached lobbying rules while working as a paid consultant for Randox, a clinical diagnostics firm, and Lynn's Country Foods in Co Down, earning £100,000 a year on top of his MP's salary.
He resigned as an MP last week.
Sir Keir has raised questions about how contracts were awarded.
He told MPs that Randox had been awarded two contracts for Covid testing equipment, with the first, valued at £133 million, for testing kits and laboratory processing.
It received an extension worth £346m to increase lab capacity over the winter.
The UK Department of Health and Social Care justified the direct award through a clause in the government's procurement policy crafted for the pandemic.
It allowed contracts to be directly awarded to a company if "only one supplier is capable of delivering the requirement, or due to extreme urgency brought about by unforeseen events".
Sir Keir said there is "obviously a concern that the use of taxpayers' money and the effectiveness of our pandemic response may have been influenced by paid advocacy" by Mr Paterson.
Randox last night told The Irish News it "will not be providing a comment".
