A last minute clause inserted into the budget for Texas will require government officials to get written authorisation before buying Windows Vista.

The clause was added by Senator Juan Hinojosa to the two-year Texas state budget, worth some $182.2bn (£123bn), and would require any state body, with the exception of schools, to get written authorisation from the state Legislative Budget Board before buying any copies of Vista or hardware with the operating system installed.

"We have a lot of problems with the Vista program," Senator Hinojosa told the San Antonio News. "It had a lot of bugs. It takes up a lot of memory. It's not compatible with other equipment, and it's supposed to be an upgrade from the XP program that is being used by state agencies, and it's not."

The clause, known as a rider, was added without objection to the budget, which is expected to be passed this week.

"Microsoft has long demonstrated a sustained commitment to Texas, which is why this development is disappointing," Microsoft spokeswoman Tonya Klause said in a statement.

"Given our daily work with government agencies and long-standing technology partnership, we are surprised that the Texas Senate Finance Committee adopted a rider which, in effect, singles out a specific corporation and product for unequal treatment.

"We hope that, as the budget continues to go through the process, this language will be removed."