The average cost of a cremation at a public crematorium has risen by a third since 2010, the BBC can reveal.
An adult cremation costs an average of £640, according to Freedom of Information responses from local authorities that run crematoriums in the UK.
The cost of new anti-pollution equipment and larger coffins have been blamed.
Critics say crematoria are being run inefficiently.
More than 170 local councils each run at least one crematorium. In other areas they are operated by private firms.
The majority said price rises were linked to the cost of installing new technology to reduce the amount of pollution, in particular from mercury tooth fillings, in response to government guidelines.
Most crematorium managers have paid between £1m and £3m to upgrade equipment to comply with new environmental rules, Tim Morris from the Institute of Cemetery and Crematorium Management (ICCM) claimed.
"Costs to cremation authorities have increased drastically," he said.
"Crematoria have had to completely replace all of their equipment to comply with changes in environmental legislation, the latest being additional equipment to filter pollutants from the waste gases."
Many local authorities run cemeteries at a loss, Mr Morris said, with the surplus money made by crematoriums subsidising burial services.
In Barrow-in-Furness, in Cumbria, the fee for cremating an adult has gone up by more than 100% - from £359 to £721.
Cost of a cremation
From Mortlake Crematorium in Richmond
Cost of cremation breaks down as follows:
£181 Spent on staffing
£163 Profit allocated to improvements
£127 Building maintenance, supplies, services and regulatory costs
£29 Fee for fuel
Keith Johnson, assistant director of Barrow-in-Furness Borough Council, said its fees were initially too low and had been brought in line with others.
"Crematoria are incredibly expensive to run, they are not cash cows," he said.
"At the time of the price rise (in 2012-13) there were 314 crematoria in the UK, we were the fourth cheapest.
"We were completely behind the market and based our new price on the two nearest crematoria."
Because it has not yet installed the newer pollutant filters, the council must pay a £53 government-imposed levy per cremation.
Mr Johnson said the crematorium was going to be refurbished over the next four years and the new equipment would be installed.
Northumberland has seen a rise from £407 to £695.
A spokesman for Northumberland County Council said the rise was in part to bring the county "more in line" with neighbouring authorities.
He said £1.8m was being invested in new air pollution control equipment to comply with "increasingly stringent environmental legislation".
In contrast, Lichfield has seen its price drop from £542 to £495, with a council spokesman saying a newer crematorium had made the service cheaper to operate.
Charles Cowling, author of the Good Funeral Guide, said prices were "absurdly high" because crematoriums were being run "grotesquely inefficiently".
He said the energy used to cremate a person cost £15 at most but prices rose when staff and maintenance were factored in.
The cost of switching the cremator on and off each day was high, he said, adding that a better system would see fewer crematoriums but ones which run day and night.
Heather Kennedy from the Fair Funerals Campaign told BBC Radio 5 live the cost of dying has "risen seven times faster than the cost of living".
A spokesman for the Local Government Authority said: "Cremations are not run to make a profit, but meeting the standards bereaved families expect requires continual investment in chapels of rest, grounds maintenance and equipment.
"Meeting environmental targets for crematoria from 2012 has meant local authorities have also had to fit expensive abatement equipment over the last few years.
"Although these factors have pushed up the price of a cremation, these costs represent a relatively small portion of the overall cost of a funeral."
The National Association of Funeral Directors is raising the issue of rising costs with the government.
Dominic Maguire from the association, which represents 80% of UK funeral directors, said costs had soared in recent years while undertakers' own fees had only risen by 3.5%.
He said: "The funeral directors' fees now account for less than 50% of the overall funeral cost."
Mr Maguire also urged people to plan their funerals, adding: "The cost of dying can come as a shock to people at a time when they are already vulnerable, and we urge everyone to discuss the issues with their loved ones and plan ahead, so that when it comes to what is a very sad and difficult time, they will at least have the comfort of having something in place."