"We need first of all to establish the facts and then to see whether the law needs changing."
TUC head of employment rights Sarah Veale dismissed the inquiry, insisting that it was clearly "politically driven".
"It is a completely disproportionate response to one or two instances. It is really quite disgraceful that the Government is pretending that there is a real public interest concern here. There isn't," she told the Murnaghan programme.
She also defended Unite's tactics in the Grangemouth dispute - including reportedly sending demonstrators brandishing a large inflatable rat to protest outside the home of one Ineos executive.
"There is a long established tradition in a civilised democracy like the UK that people can express their views in a peaceful, law-abiding way. That's what the union is doing," she said.
"They are simply disseminating information. Intimidation is a ridiculous word to use. I wouldn't be intimidated by being given a leaflet or by people standing with a large plastic rat near to my house."
Ministers have said they want Mr Carr - who will sit with two assessors, one representing the employers and one from the unions - to complete his report within six months of starting.
