By Dominic Casciani BBC News Online community affairs reporter

Immigration: Allegations of massaged figures

During 2002, there was a sharp rise in asylum applications, reaching a record number that year.

The government claims the subsequent fall through 2003 is largely down to its controversial policies.

The latest asylum statistics for the first quarter of 2004 show that trend of decreasing applications continuing.

So are the numbers genuinely drying up - or are would-be asylum seekers simply entering the UK by another route?

The NAO commissioned a team at University College London's Migration Research Unit to examine 10 different types of entry to the UK to see whether or not they could be linked to trends in asylum statistics.

The conclusions are part of its wider - but brief - report into allegations that the Home Office had massaged asylum figures.

There is no clear statistical evidence that the reduction in the number of asylum applications has had any significant impact on other forms of migration NAO report Asylum numbers 'mostly reliable'

The researchers took 10 major measures of migration - everything from tourist arrivals through to general work permits. They even looked at the rate of entry for teenage au pairs.

The team came to two general conclusions. Firstly, there is "no statistical evidence" that asylum seekers are switching their focus to other European destinations in response to tougher UK policies.

Similar falls have been seen elsewhere on the continent.

Secondly, the research found no evidence that the would-be asylum seekers had switched en masse to enter via other routes.

This does not mean that there is no link or that it is not happening; it does not mean that it is indeed happening and the government doesn't realise. It just means that, so far, nobody has found anything conclusive.

Key countries examined

The fall in applications has come from a massive reduction in arrival from 11 key countries.

At the top of that list are Iraq, Afghanistan, Zimbabwe and Sri Lanka, countries with reputations for either war, persecution or repressive regimes.

In theory, if the "disappearing" asylum seekers were trying to get in by other means, then sharp rises from these nations would be found elsewhere in immigration records.

Starting with work permits, the team found no statistical relationship between these and asylum applications.

While asylum arrivals fell by almost 35,000 in 2002-03, applications for work permits only grew by 1,597 - significantly down on previous years.

But working on a country-by-country basis, the team did not find evidence of rises in work permits applications from the same nations which had seen the greatest drops in asylum claimants.

In the case of Poland and Romania the situation is less clear. In both cases, applications for work permits did go up while asylum claims went down.

But the researchers say the figures did not automatically tally and had to be read alongside ongoing trends before the fall in asylum claims.

Other means of entry

The researchers were more cautious over applications to join the seasonal agricultural worker (SAW) scheme.

Home Office: Estimates of illegals needed

It said the patterns and trends for SAW applications did not provide "conclusive evidence" that would-be asylum seekers had been diverted into seeking entry through this method.

But if it had happened, they added, it was perhaps mainly related to would-be applicants from Poland.

The total number of overseas students fell during the period studied, including a 5% drop in students from the asylum nations being examined.

The team also concluded there was "little likelihood" of a link between former eastern European asylum seekers and work applications from new EU states - saying these were probably being driven by British employers demanding more labour.

Holes in the data

While ministers will present most of the findings as good news, there is significant criticism too.

The researchers reiterated long-standing concerns about migration statistics which many experts say make it difficult to fully appreciate what is going on.

For instance, the analysts wanted to include data collated by the Department of Work and Pensions - but could not do so because civil servants said their information wasn't good enough.

But perhaps more importantly given the ongoing political row, the team stressed that it was impossible to say whether or not would-be asylum seekers were entering illegally in large numbers because "there are neither data sources nor estimates of the number of people living illegally in the UK."

Shadow home secretary David Davies has previously suggested some of the fall in asylum applications may have been achieved by stopping immigration officials arresting illegal workers who would have then claimed asylum in an effort to stay in the country.

That's an allegation ministers vehemently deny - and the NAO has not looked at it in isolation.

But its main report did say there was a "weakness in the system of referrals of illegal immigrants".

In other words, the Home Office has no system to check whether all illegal workers who claim asylum after being arrested by the police turn up at the immigration service for interview.

How many people this applies to, we don't know. And neither does the Home Office.

In 2002 it completed a study of how other countries try and count illegals. It is still assessing whether these methods could work here - though the NAO has urged ministers to make this a priority.