Stress from a couple's parents is increasingly contributing to marriage break-ups, according to a leading divorce lawyer.

Martin Loxley, head of the Family team with national solicitors Irwin Mitchell, said parental influence was now a reason given by nearly 20 per cent of divorcing couples the practice helps.

This places the influence second only to affairs as a causal factor to divorce and contrasts with the parental pressure being cited in only 5% of cases a year ago.

Mr Loxley said, "We're finding more and more that involvement of parents helps push already vulnerable relationships over the edge. Parents tend to be at their most influential in the run up to and immediately after the decision is made to separate."

According to Mr Loxley, family strain, as the factor is known, is a exacting feature with relatives of wives and affects couples mainly in their mid-thirties and early forties, where children are typically involved and there are, often grandchildren.

Mr Loxley said, "In the majority of these cases I get involved with, it's the parents of the wife who have become involved in the relationship or acted as a catalyst for separation."

He said patterns of family life had changed in recent years and people now tended to live at home longer before co-habiting. There were therefore closer child-parent bonds than before, which could be very hard to break.

He said, "Parental influence can have a lasting impact on marriages even if it's exercised before a couple walk down the aisle. I've handled a number of cases where mothers and fathers, especially those with family businesses, have insisted on pre-nuptial agreements being signed before consenting to weddings, specifying what will happen if the couple split.

Mr Loxley quoted the wealth of parents, especially the newly-retired, as a common reason for them stepping-in after couples had taken vows, as this often allowed them to 'buy' solutions to problems.