The cost of investigating the death of Diana, Princess of Wales has jumped to more than £12.5 million, it was disclosed yesterday.

New figures show the bill for the long-running Diana inquest now stands at £4.5 million, but this is likely to increase as the hearing's last few days are not included.

After the hearing ended last week, the Metropolitan Police said it had spent £8 million in total on services arising from the inquest and the Operation Paget investigation from 2004 to 2006.

The inquest into the deaths of Diana and her lover Dodi Fayed, who were fatally injured in a Paris car crash in 1997, lasted more than 90 days and heard evidence from about 250 witnesses.

The jury returned a verdict that the "People's Princess" and her boyfriend had been unlawfully killed.

The figures revealed that taxpayers paid out £1.85 million for "external legal services", or lawyers' fees between July 1 last year and March 31.

Running costs were £768,000, video conferencing and special visits totalled £703,000, the bill for IT was £677,000 and staffing cost £234,000.

In one case, funds were used to fly an official to Los Angeles to collect a tape of a telephone conversation involving Dodi and his ex-girlfriend, Kelly Fisher.

The inquest also spent £110,000 on consultancy fees.

Yesterday's latest total also includes costs of £187,000 incurred by the coroner, Lord Justice Scott Baker, and his predecessor up to the end of June last year.

Not included in the total is the Foreign and Commonwealth Office and MI6's legal bills. Both Government departments were legally represented at the hearing and face estimated costs of up to £250,000.