Manitoba NDP MP Pat Martin is calling for a federal ethics investigation into a Conservative MP's use of parliamentary mailing privileges to promote would-be directors of the Canadian Wheat Board.

But Saskatchewan MP David Anderson, parliamentary secretary for the CWB, says there's nothing wrong with advocating for prospective board members "who will be able to work with the government" to end the grain marketing monopoly.

Anderson recently used his MP letterhead and free mailing privileges to contact some Saskatchewan grain producers to promote the "candidates that support marketing freedom."

Martin claims the mailing "clearly crosses all boundaries of decency and fairness."

"Using his mailing privileges for this purpose, that's not what your MP's mailing privileges are all about," said Martin.

He referred the letter to parliamentary ethics commissioner Mary Dawson and wants the Commons Speaker to examine Anderson's free mailing privileges.

Martin argues an endorsement on government of Canada letterhead "clearly is political interference in what should be a fair and free vote of farmers as to their choice about marketing grain."

Not true, says Anderson, MP for the Saskatchewan riding of Cypress Hills-Grasslands.

"We're letting people know who the pro-choice candidates are, the people who want to work with us to bring freedom to Western Canadian farmers," he said. "So I don't think there is anything wrong with that."

Voting for board members in five of the board's 10 electoral districts ends Friday, with the results to be announced Dec. 7. Board members are elected to four-year terms, five members at a time every two years, an arrangement intended to ensure continuity.

With files from the Canadian Press