Socialite Tara Palmer Tomkinson died as a result of a perforated ulcer and did have a brain tumour at the time of her death, her sister has said.

The 1990s 'It girl' was found dead at her London flat on 8 February three months after she revealed she had an operation on a non-malignant tumour. She was also known to have been suffering from a rare and debilitating auto-immune condition at the time of her death.

In a series of tweets, the 45-year-old's sister, Santa Montefiore, has said the coroner's report has ruled she died of natural causes stemming from a perforated ulcer.

She added: "Tara's good friends & family know that she was in high spirits in her last days. She had plans, trips & had written a moving new song.

"I've been so touched by the warm response to Tara's death. Thank you from the whole family."

Montefiore also clarified that her sister was not the goddaughter of Prince Charles as reported following her death.

In a statement, Palmer-Tomkinson's family said she will be buried during a private funeral on 27 February. The statement added: "We would like to thank the many people who have contacted us about Tara following her untimely death. It has been a source of great comfort to know how loved she was by so many people.

"Those that knew and were close to Tara knew that there was no retreat to a 'dark place' as some have disappointingly sought to suggest. In the last few weeks Tara was happy, positive and making plans for when she recovered her health.

"As usual she had been busy with the friends and family she loved, and who loved her in return. She was in communication with her family and others of whom she was fond over her final weekend and had spent a lot of her time recording music and playing the piano in her apartment - a sure sign that she was happy and feeling good.

"We will miss Tara very much and will never forget the joy, love and humour she bought to our lives."

Palmer-Tomkinson previously said she was hopeful of a full recovery following her diagnosis of the tumour.

She told the Daily Mail last November: "I got terribly frightened. I started thinking 'I'm going to die.' I actually feel very lucky. My growth was non-malignant but it affected the production of prolactin. I've been with people who have malignant brain tumours so I don't want to be like 'Hey look at me'.

She added: "I have been – touch wood – luckier. I've taken medication and, thankfully, it seems to have gone away for now."

Palmer-Tomkinson's body was discovered by emergency services Bramham Gardens. Metropolitan Police are treating her death as unexplained but not suspicious.

Tara Palmer-Tomkinson
Tara Palmer-Tomkinson at the Royal Academy of Arts Summer Exhibition in London in 2008 Gareth Cattermole/Getty Images