Prince Andrew, Sarah Ferguson splash on Swiss ski chalet

The Duke and Duchess of York bought the property as a 'family investment'. Photos / AP

Prince Andrew and his ex-wife Sarah Ferguson have splashed out on a Swiss ski chalet thought to be worth up to £13 million ($25 million).

The Duke and Duchess of York bought the seven-bedroom property in upmarket Verbier shortly before Christmas as a "family investment". The deeds list them simply as Andrew York and Sarah Ferguson.

The divorced couple were staying there last week when claims that the prince had sex with an under-age girl were made in documents lodged at a US court. Sources in Switzerland say the chalet is worth between £10m and £13m.

A source close to the duchess told the Daily Mail that she and Andrew took out a joint mortgage on the property and did not buy it outright. The development shows how close the pair are even though they separated in 1992 after six years of marriage and divorced four years later.

But it also raises questions as to how they can afford the chalet, which has up to six permanent staff, including a chef. Andrew is not known to have a vast private fortune, and Sarah only recently managed to clear £5m in debts she ran up through a series of disastrous business investments.

However, the couple have sold their former marital home, Sunninghill Park in Berkshire, which had been a wedding present from the Queen. They received £15m for it in 2007, considered to be well above its market value.

Andrew has spent around £7.5m on improvements to Royal Lodge in Windsor Great Park, where both now live, despite their divorce.

Buckingham Palace declined to comment but a source close to the duchess confirmed she and Andrew have bought the chalet jointly as a nest egg for their daughters, Beatrice and Eugenie.

"They holiday in Verbier several times each year as all the family are keen skiers and it makes sense to have their own place there."

The chalet has a master bedroom draped in furs, a living room filled with antiques, sauna, boot room, indoor pool and terrace with stunning views.

Neighbours include Sir Richard Branson and singer James Blunt.