Trade unions representing workers at companies owned by relatives of Scottish Labour leader Anas Sarwar argue that workers are being paid more than the real living wage.
Mr Sarwar’s party, which has promised new benefits for workers, has been accused of hypocrisy by political opponents after telling the BBC that not all United Wholesale employees currently receive them.
But in a statement released late on Sunday, the USDAW union said recent pay negotiations meant all staff now earn above the minimum living wage.
Anas Sarwar was not directly involved and sold his shares in United Wholesale Ltd, a company founded by his father.
The political row came after Mr Sarwar set out Labour’s plans for a new cost-of-living linked minimum wage in an interview on the BBC’s Sunday Show.
The real living wage, as advocated by the Living Wage Foundation, is currently set at £12 an hour nationwide and £13.15 in London.
This is 56p higher than the current national minimum wage, which was introduced by Labour as part of its 1997 election manifesto.
Asked whether his family’s wholesale business currently pays the real living wage, he replied: “I don’t think all of our staff get the real living wage.”
“But I do know that as a result of negotiations with the trade union, USDAW, wages have increased significantly.
“All businesses, including that one, will have to comply with new deals for workers that will deliver a true living wage across the country.”
His political opponents were quick to react to his remarks.
Stephen Flynn, Westminster leader of the Scottish National Party (SNP), said it was a “shocking revelation” and accused him of hypocrisy.
Scottish Conservative deputy leader Craig Hoy said it was “humiliating” for Mr Sarwar and “open to accusations of hypocrisy”.
But late on Sunday night a USDAW spokesman said: “USDAW has a union recognition agreement with United Wholesale Scotland and is in negotiations with the company over wages.”
“In our last negotiations we reached a pay agreement which will see all our employees earn above the real living wage.”
The spokesman added: “We urge political parties to get their act together.”
Labour sources said Sarwar was not aware of the terms of any agreement as negotiations were being held between USDAW and United Wholesale.