National minimum wage should be increased by more than the current rate of inflation, unions will tell the body which sets the rate next week.

The Trades Union Congress (TUC), the umbrella group for 58 unions, said Friday the adult minimum wage should rise by more than the retail price index (RPI) rate of inflation or the growth in average earnings, depending on which one was higher.

The Low Pay Commission (LPC) which advises the government on the minimum wage -- currently 6.08 pounds ($9.68) per hour -- is currently considering what level it should be set at from October 2012 to September 2013.

The TUC, which will meet the commission Tuesday to press its case, said hiking the rate above inflation was necessary and affordable. It added that the wage rate for 18 to 21-year-olds should also increase by the same level as that for adults.

September's RPI was 5.6 percent, its highest annual rate since June 1991.

Last year the LPC recommended a 2.5 percent increase to the adult minimum wage rate which turned out to be too modest.

Inflation is outstripping both average earnings and the minimum wage, causing a huge squeeze on living standards particularly for the low paid. ($1 = 0.628 British Pounds)

(Reporting by Michael Holden; editing by Stephen Nisbet)