Fuel costs are hitting businesses in the East of England, managers have told BBC Politics East.
One of them, a glass manufacturing firm in Norfolk, said it had seen the price of gas for its furnace triple since October.
A sailing firm in Essex said the cost of diesel had tripled, along with catering costs almost doubling.
The government has announced plans to shield firms from the effects of high energy costs for six months.
Mr Miller of Langham Glass in Fakenham said his firm required a furnace kept at a temperature of 1,140C (2,624F) virtually all year round, which used a lot of energy.
He said: “Since October, our gas price has tripled and our electricity price has doubled. This is not sustainable in the long term.”
He said he had yet to see if the capping of business energy prices for six months would help the firm out.
“Freezing the corporation tax rate will be a help, but our main focus is the energy costs,” said Mr Miller.
Colin Strachey, of Premier Sailing in Burnham-on-Crouch and Maldon in Essex, offers sailing trips and instruction.
He said the government announcement was unlikely to have any impact on his business.
“Our costs have rocketed. Fuel costs – we use red diesel – we pay £1.78 a litre. We used to pay 60p or 70p,” he said.
“We also pay extra electricity costs. We haven’t put prices up, but we will have to later in the year.”
The firm has also seen the cost of food for sailing groups using the boats rise from about £45 per group to £70.
“It is reducing our profit by about 20%. It’s significant. We only turnover £300,000 a year, but 20% of that is a lot,” he said.
“At the moment we have two permanent staff and we want to appoint one more.”
On 21 September, the government announced energy bills for UK businesses would be cut by around half their expected level this winter under a support package.
The scheme aimed to shield businesses from rising costs by fixing wholesale gas and electricity prices for firms for six months from 1 October.
Hospitals, schools and charities would also get help, the government said.
It comes after ministers announced a multi-billion pound plan to help households with bills for two years.
Analysts suggested the help for firms and households combined could cost up to £150bn.
The BBC has asked the Treasury for comment, but earlier this month the government said: “After this initial six-month scheme, the government will provide ongoing focused support for vulnerable industries.
“There will be a review in three months’ time to consider where this should be targeted to make sure those most in need get support.”