SSRS 2008 Temp Table

Hi,

Here is the what i have encountered. I have a report which uses a couple of temp tables. The reports are deployed and here is the issue. The execution time of report is changing with No.of users. If 2 or 3 users run the report at the same time, then the time taken to run the report is longer almost double.

Is it bcoz of using temp tables. Anyone encountered it before. what is the solution for this.

[Edit by moderator. Details transferred from content supplied in an answer]
@Kev Riley -- Thanks for the quick reply Here is the psuedo code.

If i replace the temp tables with temp variables, then with no of users the execution time remains the same. Any idea why this happens with only temp tables

I have 3 parameters, they are the zone, state and job type

CREATE TABLE #table1  (
            Cnt INT,
            MM INT )

CREATE TABLE #Mth (
            MM VARCHAR(6)
)

INSERT INTO #Mth(MM)
            SELECT -- (12 Distinct Months )

INSERT INTO #table1
 Select ---------
 FROM (Joins) 
WHERE -----------
GROUP BY -------------- 

SELECT * FROM #table1 -- DataSet Output

DROP TABLE (Temp Tables),

If i replace the temp tables with temp variables, then with no of users the execution time remains the same. Any idea why this happens with only temp tables