The Government has insisted that full investigations are being undertaken into the operation of offshore accounts by National Irish Bank. But it is facing strong calls from the Opposition and trade unions for new measures to regulate the financial sector and combat tax evasion.

The Irish Congress of Trade Unions (ICTU) met officials at the Department of Finance yesterday to seek major changes in the Finance Bill to tackle fraud and tax evasion.

Pressure on National Irish Bank (NIB) remains intense as the Revenue Commissioners continue their investigation of the controversial offshore accounts.

The Revenue is now thought to have moved from an initial examination of the issues with the bank to looking intensely at the scheme in question, how it worked and was marketed. The ICTU insisted there was an "urgent need" for new statutory powers to stop banks using offshore accounts as a means of evading tax.

They also called for the Revenue to be given special powers to investigate these accounts and for a watchdog outside the Central Bank to monitor the activities of the financial institutions.

However, the Taoiseach, Mr Ahern insisted the Government and its agencies were investigating the matter fully. If the Minister for Finance found the Revenue needed further powers to conduct its investigation, the Government would amend the legislation to make sure the powers were adequate, he said.

The Minister for Finance, Mr McCreevy also warned yesterday that the full rigours of the law would apply to anyone found guilty of wrongdoing.

Labour's finance spokesman, Mr Derek McDowell, called on NIB's parent, National Australia Bank, to publish the results of its internal investigations. He is also calling for the Select Committee on Finance and General Affairs to investigate banking supervision and regulation.

The governor of the Central Bank, the chairman of the Revenue Commissioners as well as representatives of individual banks would need to be called and the Compellability of Witnesses Act implemented, he said.

Fine Gael spokesman on finance, Mr Michael Noonan also demanded in a statement yesterday that the chairman of the Revenue Commissioners should answer questions before the Dail committee.

"While the Revenue Commissioners are investigating this matter, this alone will not address public concern," he said.

Meanwhile, it has been learned that most of the NIB account holders in the controversial Clerical Medical bonds were businessmen whose enterprises involved a large cash element. Two county councillors are also said to be account holders.

According to sources, many of the account holders were involved in tourism, hotels and the motor trade.

NIB itself refused to comment yesterday on allegations made by RTE that the senior management were aware of the sales of the bonds.

"NIB has no further comment to make," a spokesman said last night.

The bank still has an order preventing RTE from using or publishing information which it claims is confidential. The case is due for mention on Thursday.

It is understood that National Irish Bank account holders were approached by sales staff who encouraged more than 180 depositors to invest about £30 million in the Clerical Medical offshore bonds.

It is alleged the NIB staff targeted investors whose accounts they knew were in false names or were otherwise likely candidates for an offshore account.