The analysis of figures in 14 European countries found that Britain has by far the highest proportion of single mothers in the European Union.

The report says that in 2001, more than 8% of British households were headed by a single mother aged 18-35, while the UK also has one of the highest rates of benefits for single mothers.

In 1994 a single mother with two children who worked for about 18 hours a week could expect more than £2,000 a year in benefits. By 2001 the figure had increased to more than £3,500.

The researchers do not say outright that high benefits accelerate family break-up. Others, however, believe the study shows that generous benefits for single motherhood provide an incentive for women to have children alone.

Frank Field, the former Labour minister for social security, said: “I’ve always believed in a causal link between benefits and the number of single mothers.

“We’ve got to change so that people don’t become single mothers. For some, they become single mothers by accident, while for others it’s a deliberate choice.”

The study contrasts the situation in Britain and elsewhere in northern Europe with Mediterranean countries such as Spain, where single-mother families constitute less than 1% of the total. Spanish single mothers received £137 in special benefits a year in 1994, which by 2001 had declined to £38.

Spain, along with Greece, Portugal and Italy, have the lowest numbers of single-mother families in Europe.

Latest figures from the Office for National Statistics show single-mother families in Britain have steadily risen from 1% of all households with children in 1971 to 11% in 2004.

Libertad Gonzalez, a Barcelona academic who compiled the research, studied a sample of 6,580 single mothers from the European Community Household Panel. She estimates that for every £675 a state offers in benefits to lone parents, the incidence of single mothers goes up in that country by 2%.

After Britain, Ireland — despite its Catholic heritage — has the highest proportion of single mothers in the EU. In 2001 more than 4% of households were headed by single mothers. Irish lone mothers receive as much in benefits as their British counterparts.

Gonzalez said single mothers received more benefits in Britain and Ireland because they had “liberal” social policies where welfare payments were means-tested, which gave greater assistance to the greatest in need.

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