The Tyntesfield Estate near Bristol is up for auction in June, and has reportedly attracted interest from Madonna and Kylie Minogue.

But the National Trust wants to open the 127-year-old Gothic revival mansion up to the public - and needs to raise £20 million by mid-June to place a bid.

However, the National Heritage Memorial Fund - which helps share out cash generated from National Lottery games - has pledged to aid the campaign.

News of the fund's support has been welcomed by the National Trust's director-general Fiona Reynolds.

The house has retained many original features

Tyntesfield, a 43-bedroom listed building set in 2,000 acres of land, has been described as the "last great Victorian house".

Its contents include an extravagant collection of Victorian furniture, paintings and porcelain.

On Friday the National Heritage Memorial Fund, a public body which provides "last resort" help, promised "substantial financial support" to the trust's campaign.

Liz Forgan, chairwoman of the fund, said she could not give exact details due to commercially sensitive negotiations over the estate.

But she said: "Acquiring an estate like Tyntesfield for the public to experience and enjoy is an opportunity that may occur only once in a generation."

The trust launched its campaign to save the estate in April.

It needs to raise money from donations in order to be eligible for help from heritage grants.

But so far, it has received just £366,000 from public donations.