Its analysis of the length of time it took in 1994 to achieve a divorce injects fresh ammunition into the debate around the Government's Bill.
Far from making divorce quicker, the figures demonstrate that for most couples it will take longer.
The figures came as the latest statistics show that divorce rates fell again last year, down to 155,500, and down from a peak of 165,000 in 1993.
The office insisted yesterday that the publication of its analysis in Population Trends, just as the debate over divorce law reform reaches a climax, was "purely coincidental". But Lord Mackay's supporters will seize on the numbers to reject the argument that he is making divorce quicker and easier.
In 1994, a year that is typical of recent years according to ONS, just over half of the 158,000 divorces were granted to couples with children under the age of 16. And two-thirds of all divorces were fault based - on grounds of adultery, unreasonable behaviour, or desertion - rather than because of separation.
Couples with young children were more likely to use fault-based routes than separation, possibly because there are greater difficulties for young couples in being able to afford to separate and live apart. But the 1994 figures show more than 40 per cent of divorces are made absolute within six months of a petition being filed and 80 per cent within a year. The average was six months where the husband sought divorce and seven months where the wife was the petitioner.
Under the Bill as it stands, couples who agree to divorce and who have no children will have to wait 12 months. And where there are children under 16, the wait will be 18 months.
As a result, John Haskey, an ONS statistician said, "about nine out of 10 couples with children under 16 will have a longer wait, and for other couples, the minimum 12-month period will involve about four in five having to wait longer."
These figures measure the time from a petition being filed to degree absolute being granted - the legal process of divorce, as opposed to the time people remain married after the marriage has broken down.
8 Population Trends 84 (Summer 1996); HMSO; pounds 11.Reuse content