Divorce lawyers are bracing themselves for their busiest day of the year today with holiday pressures expected to have taken their toll on thousands of relationships.

Unhappy partners commonly cite infidelity, abuse, boredom and lack of sex as grounds for a split. And over Christmas - the peak time for cheating - a fling at the office party could provide prime grounds for separation.

Throw in family rows, financial worries and disappointing presents, and the boom in New Year divorce proceedings means those in the marital profession are now branding today D-Day, or Divorce Day.

Online advice centre InsideDivorce.com surveyed 100 UK law firms, as well as 2,000 people who were either married, divorced or separated.

It found nearly one in five of all marriages (19 per cent) was on shaky ground, with partners believing it could end in divorce.

Almost half (44 per cent) of those surveyed said their sex lives had fallen flat, while one in 10 marriages was entirely sexless.

And, according to the survey, the Midlands was the only region in the UK where people (3.7 per cent) received news about their partner's affair via text message or letter.

Family lawyer Suzanne Kingston, of Dawsons Solicitors, said men or women often came to see a solicitor without their partner's knowledge, to try to find out about their options.

The "vast majority" of people who see a solicitor end up proceeding with a divorce at some stage, she said.

More than 1.8 million couples will have contemplated divorcing their partner during the Christmas period, according to the Family Mediation Helpline.

And Relate, the UK's largest provider of relationship support, said the trend to kick-start divorce proceedings in January follows a 50 per cent surge in the number of calls over the festive period. Three quarters of New Year divorces are instigated by women.

Paula Hall, a relationship psychotherapist at Relate, said the New Year was an important time for people to assess thier lives, and couples who had already separated might decide to take the final step and divorce.