The EDM also calls on the Chancellor of the Exchequer "to recognise these actions and push employers to protect the wages of their staff".
McDonagh, Labour MP for Mitcham and Morden, said a friend who works at B&Q had told her they would be £2,600 a year worse off on the living wage, which came in at £7.20 an hour on April 1, because of bonus payment cuts for Sunday, bank holiday, summer, winter and London working. This has led to drawing up of new contracts.
McDonagh said: "Nobody is saying that George Osborne or the Government knew that this was going to be a consequence. But now we do know, they should do something about it.
"I'm sorry this is all about B&Q but that is the one we know about at the moment. The Chancellor is reducing corporation tax, that is how it can pay for it.'"It seems incredibly unfair. A lot of people are being affected in this way. Lots of companies are doing the same thing.
"For these people who work hard, and who don’t ask for anything but to work hard and try and earn a living, we are hoping to get them able to earn a decent wage.
"I want to do everything I can to help them.
"I want the government to guarantee that no one will lose money as a result of the National Living Wage. And if there are loop holes, I want the government to close them."
B&Q said it wanted to reward staff fairly with consistent pay: "No-one's base pay will be reduced at all and we are paying compensation so no-one's bonus or benefits will be reduced in the first 12 months."
B&Q added that it will retain benefits including performance bonuses, pension employer contributions and ShareSave schemes.