The French government has defended its acceptance of stolen client data, some of which was taken from HSBC's offshore banking headquarters in Geneva, saying the government had not broken any French laws, Reuters reported.

The government commented after Switzerland said this week it wanted to suspend ratification of a treaty aimed at helping France track down alleged tax evaders until it had been able to establish the facts of the case. Media reports said that Switzerland's state prosecutor had sent a letter to French authorities demanding the data be handed back by 25 December.

Members of France's ruling UMP party have attacked the Swiss decision to suspend the treaty. They have called for Switzerland to be put straight back on the OECD's so-called "gray list" of nations that have yet to fully co-operate on rooting out tax evaders, the report said.

The case comes amid other examples of Western governments – the UK and Germany – using client account data that was sold by a former employee of Liechtenstein-based LGT. While the use of such stolen data appears to be a serious breach of legal ethics, lawyers told WealthBriefing earlier this year that there are precedents for such actions under English law. However, such cases do highlight the extent to which governments are prepared to go in hunting for alleged tax cheats. Countries in the Group of 20 major industrialised nations, meeting in London earlier this year, threatened sanctions - as yet undefined - against nations deemed to be unco-operative.

The bilateral treaty with France was one of 12 signed by Switzerland to ensure its removal from the list earlier this year.

The prosecutor said a refusal to do so would violate European rules on cooperation in penal matters, the newspaper reported without giving the official's name. Swiss judicial authorities were unavailable for comment.