The biggest Irish stockbrokers and some of their smaller rivals are at odds over the value of their multimillion-euro shareholdings in the Irish Stock Exchange, the body that operates the market.

Unresolved differences over the weighting of their individual interests in the exchange have emerged as the main obstacle to the demutualisation of the highly profitable exchange before a likely move to take part in the consolidation of international exchanges.

Bigger companies such as Davy, Goodbody and NCB are on one side of the disagreement with others, including Bloxham, on the other.

The exchange is jointly-owned by seven market participants. In addition to Davy, Goodbody, NCB and Bloxham, they are: Dolmen, Campbell O'Connor and ABN-Amro. Each has an equal guarantee over the liabilities of the exchange, which is a company limited by guarantee.

This means they have equal stakes in the exchange business as it is structured at present.

The demutualisation process would convert the exchange into a company limited by shares. Such shares could be sold for a profit. That is the most likely mechanism through which the Irish exchange would take part in the round of mergers and takeovers now under way among international exchanges.

Market participants believe the Irish exchange might fare better as part of a wider group than going it alone in an international market dominated by big cross-continental exchanges.

With the Dublin market said to be worth considerably in excess of €100 million, the potential to realise significant windfalls on their interests in the exchange is a significant incentive for members to restructure the exchange.

Demutualisation has been on the agenda of the exchange since last year when the businessman Richard Keatinge produced a report on its strategic options.

But the process has been held back because the bigger stockbrokers say their dominance of trading in the market entitles them to a greater number of shares in the exchange after it demutualises.

They are understood to argue that they have made a greater contribution to the exchange and should, therefore, be entitled to a larger share of the reward from its success.

Some of the smaller players disagree, saying their equal guarantee over any liabilities of the exchange in the present structure entitles them to an equal shareholding.

"It's Davy and Goodbody versus more or less the rest.

"The process isn't going to go anywhere until that issue is resolved," said one source.

The stockbroking firms have been attempting for some months to resolve their differences, but have so far failed to find a formula agreeable to all that would enable them to proceed with demutualisation.

Some sources say the bigger firms have a larger share of voting rights at board level which creates a precedent for different share weightings.

However, no formal proposal has yet emerged along those lines.

John Maguire, a partner in Bloxham's who is also a member of the exchange board, declined to comment on the demutualisation process per se but said he was of the view that an equal guarantee was equivalent to an equal shareholding.

Exchange chief executive Tom Healy is on record as saying the organisation was examining ways of allowing member firms to sell their holdings, but said that flotation was not on the agenda.

Mr Healy declined to comment yesterday when asked about the process.