A diktat warning staff about the misuse of work mobile phones is to be issued to 750 staff at Oxford City Council.

The memo, which will explain to staff they can make personal calls as long as they are declared and paid for, will be issued to all staff with council-issued mobiles.

It is being drawn up after one individual was found to be using a work mobile to make personal calls "on a consistent basis".

The abuse was discovered after an audit of the council's leisure services department, parts of which were deemed "unacceptable".

Part of the auditor's report said: "A review of the phone bills for an individual of the team identified personal use of the phone on a consistent basis.

"Any personal calls should be paid for."

An Oxford Mail investigation has unearthed itemised phone records showing that in a two-month period last year one individual made 362 calls to three gambling lines, with more than 11 hours of calls made to one line alone.

The council does not believe this abuse is widespread and said staff in other departments had declared and paid for personal calls made on work phones.

Council staff making personal calls are supposed to pay for them, but the leisure audit found only one payment for personal calls had been made in July 2003.

Council chief executive Caroline Bull said: "There is going to be more detailed guidance on mobile use following the audit.

"Mobile phones given to staff are not for personal use.

"If we find personal calls being made we have systems in place so that the individual can pay those calls back.

"All our mobile phones bills are checked and if anyone is found abusing council property we will take appropriate action.

"We were aware of the specific problems relating to this mobile phone bill and appropriate action has been taken."

The Town Hall has a contract with Vodafone for 751 mobile phones.

Last year its phone bill, including calls, was £90,507.

According to Inland Revenue guidelines staff are allowed to make personal calls on business mobile phones because it is not a taxable benefit, so long as only one phone is given to each employee and it is only they who use it.

However, it is the responsibility of the business to monitor calls.

A city councillor, who wished to remain anonymous, added: "It's unfair the taxpayer should meet the bill, which should not have arisen in the first place and would not have arisen if the unit had been properly managed.

"The leisure business unit has, financially, been out of control."

Oxfordshire County Council has issued 2,000 mobiles to staff, which costs the authority £250,000 a year.

Itemised bills are monitored by managers and premium rate lines and overseas calls are banned.

One member of staff has been disciplined for the misuse of a mobile phone in the past five years.