The Department of Public Expenditure and Reform has twice ignored requests from the Comptroller and Auditor General to reform a special top-up system of expenses paid to politicians.

The bonus expense system allows TDs and Senators to be paid as much as €260 every day on an entirely unvouched basis when they are travelling abroad.

The enhanced subsistence rates are designed to cover the cost of so-called 'casual entertaining', and boost normal expense subsistence payments by between sixty and eighty per cent, if claimed.

The money is entirely separate to bills for flights and hotels, which are organised in advance and paid for by authorities in Leinster House.

In the summer of 2013, the Houses of the Oireachtas Service sought a review of the special payments after the top-ups were questioned by the Comptroller and Auditor General for a second time.

The Oireachtas concluded it would be inappropriate for them to reform the system however, fearing it could represent a 'conflict of interest'.

Documents obtained under Freedom of Information legislation by the RTÉ Investigations Unit reveal that they were given legal advice that politicians – as the main beneficiaries of the scheme – could not be seen to make the changes.

Instead, they asked Minister Brendan Howlin and officials at his Department to examine the top-up payments and decide what to do.

The top-up scheme can result in large payments to politicians returning from certain types of meetings overseas.

On one week long trip to Canada in 2012 for example, four TDs and Senators were able to claim an untaxed sum of more than €1,400 each on their return without providing a single receipt.

This was perfectly allowable under the rules and regulations that apply to claiming expenses for overseas travel.

The daily entitlement could potentially be as high as €262 a day, if for example a meeting of the Council of Europe was held in Paris.

On a trip to Geneva for example for an inter-parliamentary event, the entitlement would be €232 per day spent in Switzerland.

This is made up of the normal daily civil service conference rate of €145, which is topped up by 60 per cent for 'casual entertaining'.

Those rates do not include the cost of hotels, which are paid for in advance by the Oireachtas.

Documents obtained by the RTÉ Investigations Unit show how the special system of expenses had been first introduced in the 1950s.

The payments were originally designed to cover informal entertainment and what was thought to be a higher level of subsistence, which might be needed when a large conference was under way.

A memo prepared by the Department of Public Expenditure and obtained by the RTÉ Investigations Unit said that the top-ups were unique to politicians, and were not replicated in any other part of the public service.

It explained that the Comptroller and Auditor General had twice questioned the scheme as he believed it may have been in breach of separate Department of Finance guidelines.

In its conclusion, the memo said there seemed to be 'no compelling reason' to retain the special rates and offered Minister Brendan Howlin three options.

It said the rates could be retained, reduced or abolished altogether.

Instead of acting on the memo, the Department's Secretary General Robert Watt decided it was his view the Department could not get involved – referring the matter straight back to authorities in Leinster House.

That decision has now resulted in a stalemate between the Department and Leinster House with neither organisation feeling they have the authority to act.

A spokeswoman for Minister Howlin said that the question of such subsistence payments was 'a matter in the first instance for the Oireachtas Commission'.

She said: 'The day to day administration ... is a matter for the Oireachtas Commission who are in the best position to determine the best way to meet the needs of members while observing existing legislation requirements and financial resources.'

Nonetheless, authorities at Leinster House remain convinced that they are not entitled to make a decision.

A spokeswoman there said: '[We have] written again to [them], reiterating the position i.e. that it is not appropriate for Members of the Commission to decide on these matters given that they themselves are potential beneficiaries of such allowances.

'The Service has also been advised that members of the Commission involvement in such matters could give rise to potential conflicts under ethics legislation.'

They said they had again written to the Department seeking a meeting 'with a view to resolving the issues'.

In the meantime, the bonus expense rates continue to be paid.

The inaction has been criticised by Opposition TDs and campaigners on political expenses.

Enid O'Dowd, a chartered accountant who has championed transparency in expenses, said: ‘It’s really unbelievable the buck passing.

‘I think it’s quite deliberate. They’re both saying look we’re dealing with it but it’s not our problem, it’s the other guys.’

Stephen Donnelly, the Independent TD, said politicians should be treated no differently to other public servants and called for the removal of the top-up payments.

By Ken Foxe (@kenfoxe)