Britain took in hundreds of thousands more immigrants over the last decade than had previously been announced, it has emerged.

Revised figures from the Office for National Statistics showed that earlier estimates of the total number of people entering and staying in the UK since 1994 were about 400,000 too low.

New data showed that around 900,000 more people arrived in Britain to stay for longer than a year between 1994 and 2001 than left the country during that time.

This compares with an ONS estimate in November last year of 500,000 for the same period.

Of these arrivals 136,000 came from the EU, 556,000 from the Commonwealth and 544,000 from other foreign countries.

Net immigration, which discounts the number of people leaving Britain permanently, is increasing year on year and stood at 172,000 in 2001.

This has risen steadily since the mid-1990s when more people were departing than coming to the country

The revised figures, which made use of additional data not available last year, were released on the day of the Cabinet reshuffle last Thursday.

A spokesman for the ONS told Tuesday's Times newspaper that there had not been any attempt to bury the news and insisted the revision was standard practice.

"When we announced the figures last November, we had done what we could at the time, but now we have looked much more closely at the information and produced these figures," he said.

But Sir Andrew Green, chairman of controversial campaign group MigrationwatchUK, said that the ONS had acted hastily last year.

"The ONS has now admitted there was no justification for reducing net migration figures by 76,000 a year last November," he claimed.

"They arbitrarily cut the figure and now, when they have looked at the figures, they find there was no justification for that. It is extraordinary what they come up with."

Green said that the scale of inward migration by people from non-EU countries was running at a rate of more than two million people a decade.

"This means nearly 600 every day, even without allowing for illegal immigrants," he said.

"These numbers are the highest in our history, but still do not reflect the recent massive increase in work permits which still have to work through the system.

"Yet further increases can be expected from the opening of our labour market next May to the new East European members of the EU."