A logjam of appeals from the old tax system threatens to delay self-assessment.

Under self-assessment, the Revenue plans to conduct up to 15,000 enquiries each year, with at least 8,000 random audits of taxpayers' affairs. It promised accountants and taxpayers that the enquiries would be spread throughout the year.

However, most practitioners report little action from the Revenue on enquiries, with as few as 100 launched nationally, even though more than one million forms have been returned. 'The Revenue is struggling to cope,' said Richard Shooter, chairman of the self-assessment monitoring group.

The government department, which will reveal details of its enquiry plans next week, admitted that it is encouraging taxpayers to catch up with pre-self-assessment paperwork.

Elspeth May, KPMG Leicester's personal financial services partner, predicted enquiries would start in the autumn. 'We've not yet seen the Revenue raise any enquiries. It's still trying to process the returns,' she said, adding: 'There will also be a need for a training exercise to get staff up to speed.'

One practitioner said he had lodged 200 tax returns so far without an enquiry from the Revenue. But he revealed that tax collectors are still working on several unresolved appeals from former years, including one from 1990/91.

He said: 'I would be surprised if they were doing any self-assessment enquiries yet because they have not cleared the backlog.'

New research by the Chartered Institute of Taxation and the Scots ICA reveals that 73% of members fear that Revenue enquiries will become more confrontational under self-assessment, while 64% of tax professionals claim the Revenue's audit process will focus on more 'substantial' clients.