Katy Clark was sparked to action after one of her constituents drove from Ayrshire to the Inverclyde base of online retailer Amazon, only to be told he was not needed.
The MP can't understand why it is legal for companies to turn away agency staff who have already spent hard-earned cash making a journey for work.
Ms Clark said: "If a company asks you to travel to work for, say, four hours, then it should pay you to work four hours. If it says it wants you for eight hours, then it should pay you for the whole eight hours."
Amazon hires hundreds of casual shift staff every year to cover its Christmas rush.
However, as revealed by the Evening Times last week, 200 workers turned up for a 6am shift in Gourock, only to be told they would have to wait for work in the canteen, unpaid.
After our story, Amazon has decided to pay those workers. But it also admits sending workers on late shifts home early.
Workers, moreover, claim their shifts are being cancelled at very short notice.
The Evening Times has heard from staff – none of whom wish to be named – who were told at 9pm that their 6am shift for the next day was cancelled.
Agency staff also complain they have arrived in Gourock first thing in the morning after driving from Glasgow or Ayr to be told they will not be needed.
One worker said: "At least Amazon will offer you a free lunch or breakfast in the canteen if they cancel your shift.
"The agencies do not seem to care. It has not even occurred to them that they should compensate people for the cost of getting to Gourock for no work."
Ms Clark, MP for North Ayrshire and Arran, stressed recent legislation has provided more protection for agency workers, including paid holidays and sick leave.
She believes last-minute cancellations of shifts are legal only because nobody thought such practices were still widespread.
She said: "Are we going to go back to the days when people stood in a queue for work? Some of the things you hear sound as if they are from Victorian times."
In 2010 the Evening Times revealed casual workers – most of them foreign – had been told to leave Amazon's Gourock base at 2am after their shift was cut short.
Amazon is a union-free employer. It is currently facing an employment tribunal from a full-time worker who argues he was forced to quit after he tried and failed to take a union representative to a disciplinary meeting.
Amazon denies it bans its workers from being accompanied by union officials at such meetings.