Joining Europe's single currency could cost UK businesses billions of pounds in changeover costs, a cross-party group of MPs has said.

The Trade and Industry committee said the government was "unwilling even to discuss the costs of business of UK membership of the euro, let alone to estimate them".

And committee member David Maclean, a Conservative, said the costs of adopting the euro were "heading towards �38bn".

But the committee noted that the government's euro preparations unit believes the true costs will be much lower.

Margaret Beckett, the leader of the House of Commons, said allegations of a cover-up and hidden euro costs were "absolute rubbish".

Counting the costs

Adopting a new currency requires a dramatic upgrading of systems across the country, as the UK experienced when switching to decimalisation in 1971.

Replacing or upgrading computers, accounting systems, shop tills, parking meters and a myriad of other things can be a costly exercise.

In the eurozone, governments and many companies argue that the costs will be easily offset by savings on currency transactions alone.

However, firms that trade only at national or local level will have to carry the costs without experiencing immediate benefits.

Accountants KPMG guess that UK firms may have to spend five times as much on the euro as they spent on beating the millennium bug.

Several industry associations have estimated that a changeover could cost firms about 1.2% of turnover.

Some experts, though, believe that the costs will be much lower.

Vernon Ellis, the international chairman of Andersen Consulting, said surveys in EU countries and the UK suggested that the switchover would cost "no more than 0.5% of turnover".

"Our survey results ... suggest that this level of costs is generally perceived to be much smaller than the likely benefits of the euro in promoting greater European competitiveness", Mr Ellis said.

National changeover plans

The UK government has published two "national changeover plans" so far, mapping the course should the country decide to adopt the single currency.

The MPs on the trade and industry committee criticised the failiure of the plans to address the costs of introducing the single currency.

The report says that there "may be good political reasons for this, but we fear that this policy is deterring companies from preparing estimates for a changeover and may eventually increase those costs".

The committee did not say whether it was for or against the UK joining the euro.

Opinion poll suggest that about 70% of the UK population oppose adoption of the single currency.

In the business community opinions are split, with many large firms - especially exporters - in favour of the euro, while many smaller firms and, especially, retailers are set against it.