Gordon Brown insisted his action plan for tackling the financial crisis would work - despite renewed turmoil on global markets.
The Prime Minister said "hard-working families" in the UK would start to feel the benefit of efforts to bring down oil prices and ease the cost of borrowing.
But he also hit out at some retailers for failing to pass on lower oil prices at the petrol pumps quickly.
Speaking after the conclusion of a summit of EU leaders in Brussels, Mr Brown identified fuel costs and mortgage rates as key areas.
"These are the issues that we are working on every day and I believe that we will see changes as a result of the measures we are working on," he said.
Mr Brown said he was pleased that some British supermarkets have dropped petrol prices below £1 a litre, after oil costs fell to around 80 US dollars a barrel.
"But I would like to see other retailers following that lead," he said. "The average price is still £1.07 and there is still too much variation of price across our country.
"In some areas, the petrol price is still as much as £1.20 a litre. That must change."
The Prime Minister defended the Government's decision to increase its borrowing to stave off a deep recession and ease pressure on families.
"We have said that because we have got low national debt, we are in a position to borrow to keep the economy moving forward," he said.