PRAGUE (Reuters) - Czech President Vaclav Klaus vetoed the government's key pension reform bills on Monday, threatening to thwart the start of new pension funds from the beginning of the next year.

Klaus said the reform lacked wide political acceptance and it was hazardous given its impact on the budget and the economic crisis which undermined confidence in collective investment.

Klaus has lately returned several bills and is leading opposition against new tax legislation, undermining the position of Prime Minister Petr Necas, who lacks a reliable majority in parliament.

(Reporting by Jan Lopatka)