A committee of MPs has summoned Sports Direct boss Mike Ashley to be questioned about the treatment of his firm's workers.
The Business Select Committee has summoned him to give evidence on June 7 in Westminster.
Committee chairman, Labour MP Iain Wright, has already told Mr Ashley that the committee reserves the right to take the matter further if he refuses to be questioned, including seeking the support of the House of Commons in respect of any complaint of contempt.
A deadline for a response was not set in the summons.
Mr Wright wrote to Mr Ashley earlier this month saying the committee wanted to hear how he was responding to media reports about the treatment of workers and to ask what progress had been made of a review into working practices he announced in December.
"The treatment of low paid workers and enforcement of the national minimum wage are issues the committee will be keeping under review," he wrote.
Mr Ashley replied: "I was disappointed that you have adopted a stance that is deliberately antagonist.
"I believe you are abusing parliamentary procedure in an attempt to create a media circus."
Mr Ashley has invited the MPs to visit the firm's offices in Derbyshire but they want to question him in Parliament.
Unite has been campaigning against issues such as widespread use of zero hours contracts.
A spokesman for Sports Direct said: "We are extremely disappointed that the committee has apparently chosen to turn down Mike Ashley's invitation to visit Shirebrook to see things with their own eyes. We will be responding to the committee in due course."