* Teachers, municipal workers, school guards join walkout
* Labour union says reforms attacking workers' rights
* Minister says 'will not back down' (Adds minister comments, quotes, turnout)
By Renee Maltezou and Karolina Tagaris
ATHENS, March 12 (Reuters) - Thousands of striking public sector workers marched through Athens on Wednesday to protest against planned job cuts demanded by foreign lenders as unemployment in the country holds near record highs.
Teachers, municipal workers and pensioners joined the 24-hour walkout by the country's biggest public sector union ADEDY, which shut schools and left hospitals staffed by emergency workers while lawmakers debated a bill on public sector reforms.
"They won't stop unless we stop them," ADEDY said in a statement attacking the reforms as "an assault on workers' rights".
Raising mops and brooms in the air, dozens of cleaning ladies protested outside parliament, the focal point of anti-austerity protests, and high school teachers chained themselves to the metal barriers barricading the assembly.
"Traitors out of our country!" read one placard.
Anti-austerity sentiment remains high in Greece, where repeated bouts of belt-tightening since it was rescued from bankruptcy in 2010 have left three times as many Greeks jobless, pushed up homelessness and eroded living standards.
Labour unions fear Greece will have to impose even more wage and pension cuts in the coming years to meet the targets of its 240 billion euro bailout deal with the European Union and IMF.
But the minister tasked with overhauling a state sector long criticised as a hotbed of patronage jobs and overspending defended his job, branding the public sector "the sick child which, to a large degree, led us to today's (economic) crisis."
"We will not back down," Administrative Reform Minister Kyriakos Mitsotakis told parliament. "We will take the skeletons out of the closet."
Greece's lenders have demanded 11,400 public sector layoffs this year, the fifth straight year of job cuts in the sector. Unemployment stood at 27.5 percent in December, little changed from a record high 27.7 percent in October, despite signs of an economic recovery.
"We want our lives back," Maria Portelanou, a 58-year-old schoolteacher and mother of two unemployed children, told Reuters at the rally. "The government should pack up and leave."
Parties opposing austerity from across the political spectrum are expected to do well in European Parliament elections in May, according to opinion polls.
ADEDY and private sector union GSEE have brought people onto the streets repeatedly since the crisis erupted, with as many as 100,000 taking part in some demonstrations. But turnout has been low in the last year as a growing sense of resignation sets in among Greek workers.
Greece's economy has shrunk by almost 24 percent over the past six years in the deepest and most protracted peacetime recession in its history, data showed on Tuesday. (Editing by Sonya Hepinstall)