BOB Katter has condemned the racist graffiti attack on a Labor MP's office, saying his party "spits" on anyone who uses the offensive "N-word" and he had personally fought men with his fists for using such a "derogatory epithet".

Mulgrave MP Curtis Pitt discovered the graffiti attack on the front window of his Gordonvale headquarters, 20 minutes drive south of Cairns, about 8.20am on Tuesday.

Opposing sides of politics were quick to point the finger at Katter's Australian Party, arguing that the fledgling group's anti-gay ads of the previous day had inflamed the election campaign.

But Mr Katter dismissed claims his ad was anti-gay and said he had four candidates in his party who were "first Australians".

"I take that N-word very personally. I react with great rage to it. I have taken blokes out the back of the pub and rearranged their faces for using it to give them an education in racial harmony," Mr Katter said.

On Tuesday, The Courier-Mail reported that vandals had targeted Labor MP Curtis Pitt, painting the words "gay nigger loving party" on the windows of his Mulgrave electorate office, in Gordonvale.

Mr Pitt took to Twitter on Tuesday morning to condemn the attack, which came a day after the election campaign was dominated by a debate over gay marriage.

"This is the cowardly overnight attack on my office in Gordonvale. Utterly disgraceful," Mr Pitt said on Twitter.

"Whether it's graffiti like this or the shameful ads by Bob Katter, this sort of thing is NOT acceptable."

"There is NO place in Australian politics for this kind of bigotry or intolerance."

Mr Pitt, who is also Labor's minister for Aboriginal and Torres Strait Islander issues, turned up at his headquarters, south of Cairns this morning to discover the offensive slogan.

Mr Pitt took over the seat in 2009 after the retirement of his father, Warren Pitt, and holds Labor's safest seat in the state's far north on a margin of 8.5 per cent.

"It is cowardly, disgraceful, and a message of hate that cannot be tolerated," Mr Pitt told The Courier Mail.

"Myself, my staff and my wife Kerry, who is a proud aboriginal woman, are deeply upset by this.

"It is un-Australian.

"This is obviously a fringe element but there is no place in our society for this sort of bigotry and intolerance."

The father-of-two said his office had increasingly been getting hate mail including threats of physical violence.

"To see it manifest in this sort of disgraceful mess on the front window today is upsetting," he said.

"The community has condemned this behaviour as an act of cowardice. It is not representative of the fine people in this electorate."

He decried the use of the word "Nigger"

"That word is just so hurtful. We do not ever use that word in our language," he said.

"And we should all learn from the bitter lessons in the United States of that sort of unacceptable racism."

Police and forensic analysts are at the office in the main street of Gordonvale, 20 minutes south of Cairns, searching for clues that could lead to the offenders.

AT 11.30am, Premier Anna Bligh linked an "offensive" Katter's Australian Party anti-gay marriage advert to hate-filled comments scrawled across the electorate office of a Labor MP.

This morning's "distressing" graffiti attack came just one day after Bob Katter's party sparked outcry and accusations of homophobia by airing its advert.

"I think this attack, this awful graffiti attack on Curtis Pitt's office, is hot on the heels of a pretty offensive ad by the Katter party and hot on the heels of some pretty awful trash from Gavin King, the candidate for the LNP in Cairns," Ms Bligh said.

"I think everybody on all sides of politics has to be very careful in the public debate.

"In this country we like a good political debate but I think when it goes into extremes, when it incites people to hate people in our community, it's gone too far."

Mr King has repeatedly come under fire for columns he wrote several years ago as a Cairns newspaper journalist, including that women who drink to excess are party to blame for their own rape.

Ms Bligh said the use of the word "nigger" was especially offensive as Mr Pitt's wife was a "proud indigenous woman" and its use brought "a great deal of shame on those who did it".

"I say to everyone in the Cairns region: I know that this kind of language does not represent the views of decent ordinary Queenslanders," she said.

Originally published as Watch out racists, Bob will bash you