THE leader of a protest group trying to overthrow Thailand's government and scrap planned elections has called on the prime minister to either step down or be forced out.

Suthep Thaugsuban, a politician who resigned from parliament to lead the protest, and his allies have spoken of a volunteer police force, decentralisation of power and electoral reform - but apart from that have been noticeably short on specifics.

Prime Minister Yingluck Shinawatra has called an election for early next year in an effort to end the street protests but Mr Suthep, knowing that allies of Ms Yingluck's brother, ousted former premier Thaksin Shinawatra, would probably win any election, wants an unelected "people's council" to take over.

Mr Suthep said he would meet military chiefs to discuss his strategy but rejected any idea of cutting a deal with Ms Yingluck who heads a caretaker government now that the king has endorsed the election date.

She will hold a forum tomorrow to discuss reforms but says they can only be drawn up and implemented after the election.

Mr Suthep said: "Yingluck's invitations for national reform forums are nothing new. We do not accept Yingluck's offer. We won't negotiate."

The "soft way out" of the impasse, he said, was for Ms Yingluck to step down and let his council push through reforms. Failing that, the people would simply seize power, he said.