BANGKOK (AP) — Thailand’s main opposition party announced Sunday its members were resigning en masse from Parliament to protest a government they claim is illegitimate, a move sure to deepen the country’s latest political crisis.

Democrat Party spokesman Chavanond Intarakomalyasut told The Associated Press his party could not work in the legislature anymore because the body is “no longer accepted by the people.”

The minority Democrats are aligned with anti-government protesters who have staged the country’s biggest rallies in years, vowing overthrow Prime Minister Yingluck Shinawatra’s administration through mass demonstrations.

The Democrats have not won an election since 1992, and the protesters are demanding a non-elected people’s council lead the country.

Yingluck’s government came to power in a landslide vote in 2011, a ballot that observers said was free and fair.

Thailand has been plagued by political turmoil since Yingluck’s brother Thaksin Shinawatra, a former premier, was toppled in a 2006 military coup.

At least five people have been killed and at least 289 injured since the protests began last month.