That's the question which led to a heated exchange in federal senate estimates.

Member for Parkes Mark Coulton and Nationals senator Bridget McKenzie have defended themselves against claims of "trespass" made by Labor politicians over a photo taken next to a railway line in Narromine.

"To be accused of a malicious crime like trespassing is something I find offensive, especially when we made a point not to do that," Mr Coulton told the Daily Liberal.

"I have not been contacted by the Australian Rail Track Corporation (ARTC) about this and I hope that this allegation is seen for what it is, which is a politically motivated stunt."

ARTC said it would be "looking into the circumstances" around a photo and video shared to Facebook in which McKenzie and Coulton appeared to be within the 15-metre exclusion zone of the Inland Rail track.

At a federal senate estimates committee on May 23, Victorian Labor senator Linda White questioned ARTC staff on their trespass policy in relation to the post.

Senator White asked if ARTC's policy - which states that "trespassing involves unlawfully entering land which is privately or publicly owned by the rail operator" - applied to "politicians wandering onto rail corridors and infrastructure".

"We don't encourage anybody to wander onto the network," Mark Campbell, CEO and Managing Director of ARTC, said in response.

"At the wrong time, it can be a very dangerous place to be wandering around."

ARTC officials present in estimates said they did not know about Coulton and McKenzie's visit until after seeing the Facebook post.

McKenzie told estimates that she and Coulton "sought permission" from the minister for the site visit but were "denied". She said the resulting picture was on a level crossing on "a public road" and therefore wasn't trespass.

Mr Coulton agreed.

"These are petty accusations which add insult to the injury of being refused entry onto the site of a project which was begun under our Government," he said.

"Senator McKenzie and myself took the video in question at a level crossing intersecting Narwonah Road, which to our knowledge was a public area.

"We respected the Minister's wishes not to enter the ARTC construction site, however being formally refused entry meant that if we were going to get any footage of that area we had to stick to public roads."

Mr Coulton said the intention of the visit was to show progress on the Inland Rail line and highlight the impact stalled progress could have - concerns which Ms McKenzie questioned ARTC officials on in estimates before the trespass accusation was lobbed.

"We were there because I wanted to show the Shadow Minister for Infrastructure Senator McKenzie the work which had already been completed on the Inland Rail between Narromine and Narrabri," he said.

"I wanted to show her this important piece of nationally significant infrastructure and highlight the need for this project to be continued."

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