The paper says it is putting up the reward in the hope that someone will come forward with a vital clue in the hunt for the person who murdered the BBC television presenter.

Ms Dando, 37, was shot in the head on the doorstep of her home in Fulham, west London, on 26 April. Police are still following up leads in their hunt for her killer.

The BBC's Tony Morris: "The money may provide an incentive"

The Daily Mail announced the reward on its front page on Thursday, and said it had taken the "unusual decision" after "lengthy consultation" with the family and senior Metropolitan Police officers involved in the case.

It said it had the full backing of the Dando family, and quoted Ms Dando's brother Nigel as saying: "I am very pleased about the Daily Mail's positive action and hope it will lead to the arrest and conviction of whoever is responsible for my sister's murder."

An E-fit of the suspect

The newspaper also quoted Detective Chief Inspector Hamish Campbell, who has been leading the case, as saying: "I believe this sum of money might just trigger someone who knows the true story of what happened on that day to get in touch and tell us.

"This is an extremely large reward and shows the determination of the Daily Mail to assist the police and the public to identify whoever killed Jill Dando.

"With a sum as large as this we sincerely hope it brings that vital piece of information that will quickly resolve this investigation."

Also on Thursday, Scotland Yard named the new detective leading the murder hunt. He is Detective Chief Superintendent Brian Edwards, who heads CID operations in central London.

Investigation strategy

He has now been put in overall charge of the case above Mr Campbell, but a spokeswoman insisted the move in no way implied criticism of Mr Campbell.

Mr Campbell remains in daily charge of the 50-strong inquiry team while Mr Edwards will direct the strategy of the investigation.

Mr Edwards, who led the inquiry into the killing of London headmaster Philip Lawrence, appeared at news conferences in the early days of the Jill Dando murder inquiry before handing over to Mr Campbell.

The Daily Mail's reward is offered for information directly leading to the arrest and conviction of Ms Dando's murderer.

Anyone with information should phone the incident room on 0181 246 0732 or Crimestoppers on 0800 555 111.

The Daily Mail says people can also contact its crime desk on 0171 938 6094.