LONDON (AFX) - Headline UK retail prices (RPI) in June are expected to have risen an adjusted 0.1 pct from May and 1.8 pct year-on-year, according to the median of 21 analysts' forecasts compiled by AFX News. May RPI was up an adjusted 0.6 pct month-on-month and was 2.1 pct higher year-on-year. Underlying inflation, RPI excluding mortgage interest payments (RPI-X), is forecast to have risen 0.1 pct month-on-month for a 2.3 pct increase, following a 0.8 pct monthly rise and 2.4 pct annual increase in May. RPI-Y, which also excludes indirect taxes and excise duties, is expected to have risen 0.2 pct month-on-month for a 2.6 pct annual increase. May RPI-Y rose 0.9 pct month-on-month and 2.8 pct year-on-year. June retail price data are released on Tuesday, July 17th.