ISTANBUL, June 19 (Reuters) - Turkey's main opposition party filed a motion to parliament on Wednesday saying that adjustments to the methodology used by Turkey's Statistical Institute (TUIK) when calculating inflation were unprecedented and damaged credibility.
In the motion requesting a response from Finance Minister Berat Albayrak, Republican People's Party (CHP) lawmaker Gursel Tekin asked whether he had requested that TUIK limit the rise in inflation "fictionally".
"Since salary raise rates are linked to the rise in inflation, when the announced number is not in line with the real inflation, millions of employees are wronged," he said in the text of the motion.
"Unprecedented practices in April inflation data damages the credibility of the (TUIK) institution," Tekin said in his motion.
According to TUIK data, annual inflation slowed to 19.5% in April, on a declining trend since it hit its decade high of 25% in October last year following the lira crisis.
The median estimate in a Reuters poll at the time put the annual CPI at 20.33%. The higher-than-expected fall had led to speculation among analysts at the time that the institution had manipulated the numbers.
TUIK said at the time that suggestions the institution's statistics were not correct or had come under political influence did not reflect the truth.
TUIK declined a Reuters request for comment on the CHP move. The Finance Ministry was not immediately available for comment. Parliament's bylaws require that the minister respond in 15 days, but the process generally takes longer.
In his complaint, Tekin cited an irregularity in the parts of the data dealing with shoes and clothing, as well as automobiles. He added that analysts believed that the changes in the two components could affect inflation by 0.5 percentage points.
He said the quality adjustment on the clothing index, which was previously around 0.2%, was calculated as 4% in April's data, which he said was "known to be impossible". Such adjustments, based on judgments of the quality of the items in the inflation basket, are generally very low to attempt to maintain the usefulness of the comparison in the data.
Official inflation statistics are used in several areas, including calculating salary increases and house rent raises. (Reporting by Orhan Coskun; Writing by Ezgi Erkoyun; Editing by Jonathan Spicer and Alison Williams)