LONDON, May 24 Reuters Britain39;s high inflation rate fell by less than expected in April and a closely watched core measure of price growth surged to a 31year high, according to official data that will cement bets on more Bank of England interest rate hikes.

The consumer price index rose by 8.7 in annual terms in April, leaving Britain with the joint highest rate of inflation among Group of Seven advanced economies along with Italy.

Economists polled by Reuters had forecast that the headline CPI annual rate would drop to 8.2 in April, moving further away from October39;s 41year high of 11.1.

Earlier this month, the BoE forecast inflation of 8.4 for April.

With inflation proving stickier than the Bank expected, it now seems all but certain that the Bank will raise interest rates from 4.50 to 4.75 in June and perhaps a bit further in the months after, Paul Dales, chief UK economist at Capital Economics, said.

The BoE is due to announce its next decision on rates on June 22 and after Wednesday39;s data investors were pricing the likelihood of another quarterpercentage point increase in borrowing costs next month at 100, up from 83 on Tuesday.

Sterling rose against the U.S. dollar and the euro after the figures were published before giving up some of those gains.

Core inflation, which excludes energy, food and tobacco prices and price growth in the services sectors which is also watched closed by the BoE to gauge the persistence of inflation both hit their…