SPECIAL state security police are monitoring West Australians in internet chat forums and on blogs, as operations intensify in the leadup to October's Commonwealth Heads of Government Meeting.

The Sunday Times has learnt the Big Brother-style security extends to any open posts on the web and are likely to include Facebook and Twitter.

The crackdown was revealed after State Security Investigation Group officers this week visited a former history teacher and told him they were monitoring his pro-republican blog. In it, Mark Tomkinson had joked about dropping green and gold paint on Kate Middleton at the royal wedding.

Mr Tomkinson said the officers drove 270km from Perth to his Bridgetown home for the visit, which he believed was intimidation ahead of CHOGM an event that will bring the Queen, Prince Philip and the leaders of 53 commonwealth nations to Perth.

He said it was a "disgrace" and "un-Australian" that police could pressure law-abiding citizens for exercising their right of free speech.

"

,

he said.