Bangkok: Thai Deputy Prime Minister Chavalit Yongchaiyudh on Tuesday resigned saying he accepted responsibility for clashes between police and protesters that injured 69 people.

"Since this action did not achieve what I planned, I want to show my responsibility for this operation," Chavalit, a former prime minister who was appointed to mediate with the anti-government protesters, said in his resignation letter.

Thai riot police fired teargas at protesters outside parliament on Tuesday, injuring 69 people, as campaigners opened a new front in their four-month bid to unseat the government.

Some protesters were badly hurt, including two men who had part of their legs blown off by exploding gas canisters when police moved to clear a path through the barricades for Prime Minister Somchai Wongsawat.

The protesters from the People's Alliance for Democracy (PAD) regrouped in front of the parliament building, chanting slogans to try to disrupt Somchai's maiden policy speech.

The PAD has occupied the prime minister's offices at Government House since late August, forcing Somchai to run the country from Bangkok's little-used Don Muang airport.

Outside parliament, a phalanx of riot police seven-deep faced several thousand PAD supporters, many of them wearing masks and swimming goggles in case of another tear gas attack.

"We will be here all day today. We will fight here," Sirichai Mai-ngam, one of the PAD's leaders, said on radio.

The legislative session got underway despite the building being on standby power after protesters tore down power lines.

The PAD, a coalition of businessmen, academics and activists, accuses Somchai of being a political proxy for former premier Thaksin Shinawatra, his brother-in-law, who was removed in a 2006 military coup.

Somchai has tried to open a dialogue with the PAD since he replaced Samak Sundaravej, who was removed last month by the courts.