Ms McKenzie was responding to claims from Member for Bendigo Lisa Chesters that she did not support giving MPs and senators the right to vote freely on the issue.

In 2011, Ms McKenzie spoke of her opposition to same sex marriage and has maintained the same opinion four years later.

She said she would vote against a bill legislating same sex marriage should it come before the Senate.

"As a National Party senator, every vote which comes before the Senate is a conscience vote for me and I will be voting with my conscience to oppose any such bill which seeks to legislate for same sex marriage," Ms McKenzie said.

"I have never opposed providing MPs and Senators the right to a conscience vote on this matter.

"I strongly support the recognition of same sex relationships through civil unions and have long advocated for an end to discrimination based on sexuality, however I believe marriage is a sacred commitment between a man and a woman and should remain as such."

The Australian Marriage Equality website listed Ms McKenzie as "undeclared or undecided" on the issue, while Ballarat-based Senator Michael Ronaldson was listed as opposed to same sex marriage.

Member for Bendigo Lisa Chesters said the two senators were "out of touch... with the views of the local community".

"The public declaration from local small businesses of their support for marriage equality is another example of how the majority of Bendigo and central Victorians feel about this issue," she said.

"I strongly believe the numbers are there to support marriage equality, if all MPs and senators are given the chance of a free vote."

Labor has been pressuring the Liberal Party to allow MPs and senators to have a conscience vote on the issue since Bill Shorten introduced a bill to parliament legislating for same sex marriage last month.