The first official figures released from the Office for National Statistics (ONS) show that in the lowest groups as few as 3% have home access, compared with up nearly 50% in the higher groups.
Regional differences are a strong factor in the level of access, with London and the South East leading the way, but internet use has doubled in most other regions in the past year.
At the lowest end of the scale were Northern Ireland at 11%, and also Scotland and the North East, which both stood at 14%.
Drawing its statistics from the Family Expenditure Survey, the ONS also reveals that the presence of children greatly increases the likelihood of families having home access to the web.
More than 25% of homes in the UK now have access to the internet, with the first three months of 2000 showing an average of 6.5 million households logging on from home.
Taken an average for the 12 months from April 1999 to March 2000, says the ONS, the figure drops to 19%.
Income a strong factor
But levels of internet access still relate very strongly to income and region, says the report, which marks the first of a series of quarterly reports tracking access across the country.
Figures reveal that internet access doubled in every region except London, although the increase in the capital was still very substantial.
In 1999-2000, proportions were highest in London at 25%, the South East at 24% and the East of England, at 22%.
But income levels are still a strong governing factor in whether people are able to log on or not.
In 1999-2000, says the ONS, access was low in all four of the lowest income groups, at around 3% to 6%.
Splitting household income into 10 different groups, the report shows that from the fifth group onwards levels increased rapidly with income, to 48% for households in the highest group.
The level of access in the lowest income group may be higher than in the next two groups due to the presence of student households.
The pattern of unequal access was broadly the same as for the 1998-1999 period, although the middle to moderately high income groups (fifth to seventh groups) showed a significantly larger growth from a low base.
Children log on
While retired households were the least likely to have internet access, the presence of children significantly boosted the figures.
The largest increase in access compared with 1998-99 was among couples with one or more children, where numbers more than doubled.
There was also a substantial increase among
couples without children and below retirement age, with an estimated 26% having access.
In 1999-2000, households with two adults and one or more children had much the highest levels of internet access, 31% cent if there was one child and 35% if there were two or more.
Much lower proportions of one parent households had internet access - 7% if there was one child and 11% if there were two or more.
Retired households were the least likely to have access, with around 5% of couples and 1% of one person retired households logging on.
The survey was based on 7,000 households in the UK.