UPDATE 3.15pm: TRUCK drivers and their supporters today claimed a denial of democracy when their big rigs were denied access to the front of Parliament House for an anti-carbon pricing rally.

But they left police baffled when they claimed officers had blocked hundreds of trucks in the Convoy of No Confidence from even entering the Australian Capital Territory.

Some 300 anti-carbon pricing protesters gathered in Federation Mall, in front of Parliament, to hear from Liberal MPs including Opposition Leader Tony Abbott, and the Nationals Barnaby Joyce.

Senator Joyce urged the rally to telephone Labor MPs and demand they vote against the Government's carbon pricing legislation when it is introduced next week.

"So I ask those members who are considering voting for this carbon tax to do the honorable thing and cross the floor," he said.

"I'm asking them to do one thing. I want them to walk 10 feet for our nation and cross the floor. Walk 10 feet for our nation."

Numbers were well down on last Tuesday's rally against carbon pricing although Senator Joyce said some truck drivers were "out there riding round and around like Indians".

Broadcaster Alan Jones said the smaller-than-expected crowd was because "thousands" of people had been blocked from attending the rally and that "hundreds" of trucks in the convoy had been stopped at the border as they tried to enter Canberra from New South Wales.

"This is the most disgraceful thing that has ever been done to democracy," Jones told the rally.

"The people who have come here can't actually get into the precinct to be heard."

media_camera Broadcaster Alan Jones addresses protesters at the Convoy of No Confidence rally in Canberra. Picture: AAP

Alan Jones addresses the rally. Picture: AAP

A spokeswoman for Canberra police told news.com.au and other outlets no trucks had been stopped at the border, and no people had been prevented from attending the rally.

Trucks were barred from a short section of Parliament Drive, a link road immediately in front of the building, as agreed with the rally organisers.

Last Thursday, the officials who run Parliament House re-sent a week-old alert to staff saying "the Australian Federal Police have been working with the organisers of the event to maintain access to Parliament House for Senators, Members, other building occupants and visitors".

It said: "It is expected that the protest will attract a large number of people to Federation Mall.

"At times there may be long queues of people entering Parliament House via the public entrance.

"In order to manage pedestrian safety in this area, the Parliament Drive link road across the tip of Federation Mall will be closed from 6am to approximately 6pm on both days."

Safety would not have been the only concern. In 1995 logging industry truck drivers occupied Parliament Drive with the vehicles and forced Prime Minister Paul Keating to walk to work.

Today, some in the convoy left their trucks at showgrounds on the edge of Canberra city, while others circled the base of Capital Hill honking their horns.

Hundreds of trucks from as far away as Western Australia arrived in Canberra last night.

The truckers in 11 convoys are demanding a new election and protesting about the government's approach to live animal exports, the carbon tax, mining tax, gay marriage and road laws.

Some have complained about Finance Minister Penny Wong and her lesbian partner having a baby.

Ms Gillard's office last night said the Prime Minister had no plans to meet the protesters at this stage.

Mr Abbott yesterday climbed aboard one of the trucks in a convoy of 20 to 30 vehicles for the last leg of the journey into the nation's capital.

"They are very decent, salt of the earth Australians who feel that they've been ripped off by a bad government," he said.

Mr Abbott said the truck has a "no carbon tax" sign on its front and the drivers were "blue collar battlers" spending $500 of their own money on fuel for the drive to Canberra.

Mr Abbott said Ms Gillard should meet the truck drivers, saying former PM John Howard had met footballer Michael Long on his walk from Melbourne even though he wasn't a fan of the PM.

"She seems to think that if you don't agree with her you're some kind of extremist and I just think that's dead wrong," Mr Abbott said.

Some major trucking groups have distanced themselves from the protest which is being led by National Road Freight Association president Mick Pattel.

Mr Pattel was preselected as a Liberal-National candidate for Mount Isa for next year's Queensland state election but stepped aside after facing pressure for some radical views. He said climate change was a international conspiracy to force a "new World order".

Treasurer Wayne Swan said the truck drivers were "free to express their opinions in any way they like as long as they do it lawfully".

Greens leader Bob Brown said the truck drivers had a right to protest but they seemed to be short-sighted.

"It seems like the prime qualification to be there is to be angry about something - these are Abbott's angry people," he said.

Originally published as Shock jock's claim of protest blockage denied