New Democratic Party (NDP) leader Thomas Mulcair speaks during Question Period in the House of Commons on Parliament Hill in Ottawa December 12, 2012. REUTERS/Chris Wattie

OTTAWA - NDP Leader Thomas Mulcair says a Conservative backbencher's bill to force unions to disclose how they spend their money is little more than a bone being thrown to the right-wing base of the Conservative and has little success of surviving a court challenge.

In a wide-ranging year-end one-on-one interview to be broadcast Thursday at 6 p.m. ET on Sun News Network, Mulcair's dismissed the bill, brought forward by B.C. Conservative MP Russ Hiebert, to force more transparency and accountability in Canada's unions.

"What (Hiebert's bill) is about is trying to make life difficult for organized labour in Canada. Let's be transparent about that," Mulcair says in the interview.

The bill passed the House of Commons Wednesday night.