Staff at the taoiseach's office who called premium-rate lines on their work mobile phones are to be asked to refund the cost.

An investigation into the use of the phones at the Department of the Taoiseach also found that 27 of the 205 staff who were given a state phone did not actually require one, and had to have their accounts shut down.

The department said 178 people still had taxpayer-funded mobiles, which included 48 phones in the government press office, 26 in the taoiseach's private office and eight for former taoisigh.

An analysis of mobile phone costs from January to mid-July of last year found that the total bill was €62,243, meaning the yearly bill for the department is well over €100,000.

Of that, the largest bill was from the press office, with €11,336 spent on mobile calls, while the bills for former taoisigh came to €3,434.

An analysis of all calls and texts last April and May showed that at least five people had invoices that were "not compliant".

The report said: "Three were in respect of premium-rate text services and two for UK personal calls."

It also said another phone had been used for downloading information which could not be considered to be work-related and said this was "prohibited".

The report said: "[The department] should amend the mobile phone policy to reflect the position regarding premium-rate numbers and arrange to recoup all personal charges identified during the course of the audit.

"Staff members who have been identified as subscribing to premium-rate text services should be instructed to cancel their subscriptions immediately."

A copy of the audit findings, released under the Freedom of Information Act, said banning premium texts or numbers was not feasible because it could interfere with certain types of calls or texts that were legitimate.

It also said there appeared to be a lack of monitoring of mobile phone bills in the department.

The audit report said certain staff must have their mobile bills paid by the exchequer because they were frequently away from their desks on official business.

A mobile phone policy states, however, that misuse of the phone could lead to disciplinary action.

It says: "It is accepted that calls incidental to an officer's work which are made to home... which arise because of an officer's absence from the office on official duty are not classed as private calls. Calls to premium-rate telephone numbers, and downloading information from non-work-related sites are, however, prohibited."