HOUSTON—Despite a constitutional ban on legislative bonus pay, state senators have paid out over $650,000 in temporary pay increases to top aides over the last two years.

The senators defend the practice. But critics say the end-of-year pay increases, bumping salaries over $10,000 a month in some cases, are designed to get around the prohibition, according to a story in Sunday editions of the Houston Chronicle and San Antonio Express-News.

“While most Senate staff deserve better compensation, raising their pay scale for a single month can only be considered a ’bonus,’ which is prohibited under the law,” said Craig McDonald, director of the liberal watchdog group Texans for Public Justice. Relying on records obtained by the Texas Public Information Act, the newspapers found a pattern in which senators inflated salaries toward the end of a fiscal year, then reduced them several weeks later. Most senators have granted at least one increase that could be seen as a “bonus.” Others engaging in the practice to varying degrees include Houston-area Republicans Dan Patrick and Tommy Williams, and Democrats Mario Gallegos and Rodney Ellis. Democratic Sens. Leticia Van de Putte of San Antonio and Kirk Watson of Austin also used part of their $37,000 monthly budget allocation on temporary pay increases for aides. Some senators say the extra money helps them retain talented employees. Others say salaries are kept low most of the year to avoid a big budgetary surprise, noting that the temporary pay increases are awarded only if there’s money left over at the end of the fiscal year.