Alexandre Vinokourov is the defending Tour of Spain champion

The move comes after the team were thrown off the Tour de France last month when leader Alexandre Vinokourov tested positive for blood doping.

Fellow Kazakh Andrey Kashechkin failed the same test last week. And German Matthias Kessler tested positive for testosterone before the start of Tour.

The Vuelta organisers described the failed tests as "deplorable mistakes".

"We have decided to withdraw the team's invitation for La Vuelta because of doping cases within the team during the 2007 season," a statement from the race organisers said.

"We are convinced the team's directors are interested in finding out who is responsible for these deplorable mistakes.

Both Kessler and Vinokourov were sacked after returning positive B samples while Kashechkin is awaiting the result of a second test and will also be dismissed if he tests positive for the second time.

Astana suspended their activities immediately after Vinokourov's test result.

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The Vuelta organisers praised Astana's decision to suspend the two riders, but the statement added: "The urgency of the dates [of the start of the race] do not allow us to push this decision back any further."

In its previous guise of Liberty Seguros, the team was forced to pull out of last year's Tour de France because it did not have enough riders to compete.

A number of its riders were caught up in the Spanish police investigation into doping in cycling known as Operacion Puerto, which has implicated more than 50 riders.

The three-week race around Spain begins in Vigo on 1 Sept.

It will take place without Tour de France winner Alberto Contador and fellow Spaniard Alejandro Valverde, who have decided not to compete.