Princess Diana's final resting place is to undergo a multi-million pound facelift following criticism that her grave in Althorp has fallen into neglect.

The island where the Princess is buried and the lake surrounding it are to be re-designed to mark the 20th anniversary of her death next year.

The project will be led by her brother, Earl Spencer, who has faced criticism in the past for allowing the burial site to become overgrown at the centre of his 13,000-acre estate in Northamptonshire.

An announcement on the Althorp website describes the “ambitious” project as “the first major revamp of the gardens in 350 years”.

It said: “The Oval Lake where Diana, Princess of Wales, was laid to rest on September 6, 1997, is undergoing an extensive re-design to honour her memory.

“It will be completed in time for the 20th anniversary of her death, in August 2017.

“The island at Althorp is in the process of undergoing extensive re-modelling, along with the rest of Althorp's gardens.”

Earl Spence's third wife Lady Karen, whom he married in 2011, will oversee the re-vamp, which will constitute the first transformation of the grounds since they were designed in the 17th century by Andre Le Notre, King Louis XIV of France's principal gardener who also masterminded the gardens of Versailles.

It follows criticism by Diana's personal chef Darren McGrady that her final resting place had become neglected.

After visiting Althorp in August 2014, he posted a series of pictures of the algae-covered lake on Twitter, along with strongly worded comments calling on Earl Spencer to take action.

One read: “Sad to see Earl Spencer has neglected Diana's resting place,” while in another tweet the chef, who cooked for Diana at Kensington Palace from 1993 to 1997, implored: “Please tidy up the vegetation on the island”.

News of the alleged neglect was revealed by the Sunday Express and the controversy went on to make headlines around the world.

At the time Althorp responded by admitting that algae was a problem but insisted that the burial site, which also includes a small temple where visitors can pay their respects, was being properly maintained.

Responding to reports a year later which claimed nothing had changed, a spokesman for Althorp said the grave was swathed in flowers and foliage because it had become “part of the ancient landscape over time”.

The natural growth of greenery was said to “intentionally lend privacy to the Princess's final resting place”.

Visitors pay up to £18.50 to enter the 500-year-old estate, although there is no public access to the island itself.

It has never been revealed exactly where on the island Diana is buried.

The Althorp renovation comes after it was announced in March that Prince William and Prince Harry will honour their mother with a new memorial garden at Kensington Palace to mark two decades since she was killed in the Paris car crash.

The garden will open next summer alongside a new exhibition inside the palace where the princes grew up and William and Kate now live with Prince George and Princess Charlotte, a few doors down from Harry.

Although she will always be synonymous with the palace in west London where fl oral tributes piled up in the aftermath of the crash in Pont de l'Alma, Althorp has been the Spencer family seat for 18 generations.

When her father John Spencer inherited the title of Earl Spencer in 1975, the then Lady Diana Spencer and her family moved there.

Since her father's death in 1992, the estate has been operated by Diana's younger brother Charles, the ninth Earl Spencer, who delivered the moving eulogy at her funeral.

Dating back to 1508, the estate also features 38 oak trees that were planted to symbolise every year of Diana’s life.

Hundreds of white roses and white water lilies were also planted after her death.

An exhibition entitled Diana: A Celebration ran at Althorp from 1998, featuring hundreds of her personal possessions and clothing, including her spectacular royal wedding dress, designed by David Emanuel, with all profits going to the Diana, Princess of Wales Memorial Fund.

When it closed in 2013, all the exhibits were returned to her sons.

In February, some of Diana's iconic dresses went on show at Kensington Palace alongside outfits of the Queen and Princess Margaret in the Fashion Rules Restyled exhibition.

Last week Harry, 31, spoke about the “gaping hole” left by his mother's death.

He said: “All I want to do is make my mother incredibly proud. That's all I've ever wanted to do.”

Express