Secret liasions is one of the reasons marriages break down

The study by the InsideDivorce.com website said affairs were blamed for relationship difficulties by 50% of those taking part from Northern Ireland, compared to an average of 27% across the UK.

Relate Northern Ireland chief executive Gerald Clarke said: "There is a lot of economic hardship and the aftermath of the Troubles leaving a lot of people scarred as a result of what has gone on.

"While it is being brushed under the carpet, it still leaves a scar."

Apart from secret liaisons, money and couples in loveless marriages, other causes of separation included domestic abuse, lack of sex, stress caused by Christmas breakdown in communications.

In 2006, just under 2,600 marriages ended, the largest tally yet.

For couples married in the mid-1980s, an estimated one-in-six relationships ended by the 20th wedding anniversary.

The stress of Christmas is one of the reasons for divorces

Researchers said 60% of divorcees counted boredom as a flaw in their marriage, compared to 29% in the rest of the UK.

Domestic violence was less of a problem in Northern Ireland, with one-in-10 highlighting abuse.

Northern Ireland people were more likely to suffer emotionally, with one-in-two left a wreck by the separation. Only 10% cited lack of sex as an issue.

The days after Christmas are among the busiest for divorce lawyers, with a stressful Christmas often the final nail in the marital coffin.

Most divorces at this time of year are instigated by women and more infidelities are committed during the Christmas party season than at any other time of the year.

Mr Clarke added: "Christmas is always a stressful time when it comes to relationships because of the myth presented by the media that puts individuals and couples under enormous emotional and financial pressure to live up to the image created.

"Most people can't afford it or are disappointed because their expectations are not being fulfilled."