The committee called Labour's Ian McCartney, Tory John Greenway and Liberal Democrat Nick Harvey to appear on Thursday morning, shortly after PRWeek went to press.
McCartney, a former trade and industry minister, is paid £115,000 a year for advising Fluor, one of the world's largest nuclear companies.
The US multinational is currently bidding for a £5bn contract to run Sellafield, Britain's biggest nuclear site.
According to the House of Commons Register of Members' Interests, Greenway receives up to £10,000 for his role as a 'consultant to the Tote, providing advice on public policy in relation to horseracing'.
He has also registered up to £15,000 in fees for his work with the Institute of Insurance Brokers.
Meanwhile, former PR man Harvey receives up to £10,000 from PR agency Trimedia for being a 'communications strategies consultant'.
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