Prices are rising at their fastest rate in 40 years.
In the 12 months to April, UK inflation rose to 9%, up from 7% in March.
Millions of people saw a 700-a-year increase in energy costs last month.
Inflation is expected to rise this year due to higher fuel and food prices.
The rise in inflation in April was caused by higher energy bills.
A higher energy price cap kicked in last month, meaning homes using a typical amount of gas and electricity are now paying more.
The Office for National Statistics said the price of food, transport and machinery drove up the inflation rate.
The rate at which prices are rising is called inflation. Milk inflation is 5% if the price of a bottle of milk increases by 5p.