The research shows just 79 per cent of BT customers are satisfied overall with their home phone provider, compared to 92 per cent at the top-rated company, TalkTalk. Only NTL fared worse in the survey, with 73 per cent of customers saying they were satisfied.
Uswitch said BT had scored particularly badly on price, with 44 per cent of the company's customers saying they did not believe they were getting value for money. The top-ranked telecoms company on price - TalkTalk again - scored a 90 per cent satisfaction rating on the same issue.
The survey comes at a particularly difficult time for BT, which is under increasing pressure from rival home phone service providers. Last week, telecoms regulators told the company to cut the price it charges rival suppliers for home phone lines, which will enable them to lower the prices they charge customers when renting out the lines.
Jon Miller, a Uswitch director, said BT was losing 90,000 customers a month, though it still has more than 18 million customers using it at least for line rental. Of these, 14 million say they would recommend the service.
"It is interesting to see that the companies with the most customers have been exposed as the worst offenders when it comes to customer satisfaction," Miller said.
However, John Petter, chief operating officer of BT Retail, claimed the Uswitch survey was flawed because the research was conducted online.
"The survey has major flaws but we're still heartened that 14 million customers - more than any other company in the survey - would recommend us," Petter said. "As the incumbent, we have to try harder than everyone else."