The assembly government had given the garden over �1m Timeline: National Botanic Garden 'Optimism' over garden's future

The announcement on Wednesday by Welsh Culture Minister Alun Pugh, is the latest in a series of blows against the attraction in Llanarthne, Carmarthenshire, which has suffered as a result of low visitor numbers.

A statement from the garden's trustees said they were "deeply disappointed" and the lack of help would lead to liquidation - a meeting on Monday would be called to "formalise the necessary arrangements".

After a promising start when it opened in 2000, visitor numbers at the attraction have slumped and it has been kept afloat by emergency handouts.

Responding to a 21-point plan put forward by the trustees last week, Mr Pugh said the request for further help was "unacceptable" and he did not believe it would help.

He told the assembly chamber: "The decision on the future of Middleton now lies with the board of trustees.

Middleton facts First national garden built in Britain for 200 years Full name: Middleton, the National Botanic Garden of Wales Cost �43 million to set up 568 acre site Glass dome designed by Sir Norman Foster Houses many threatened plants, particularly Mediterranean Funding included �21.6m lottery money

"They are clearly in a very precarious financial position and will need to consider carefully their responsibilities."

But, he added, the assembly government remained committed to helping the long-term future of the site.

He said: "Several potential investors have already expressed interest. We stand ready, together with our public sector partners, to work with any organisation that has viable proposals for taking forward the garden."

But his words were met with derision from opposition party Assembly Members.

Many feel the assembly government should have done more to help the gardens - the centre piece of which is a giant glass dome designed by Sir Norman Foster.

Middleton used to employ around 100 people

Plaid Cymru's Rhodri Glyn Thomas AM said it was bad news for the economy of Carmarthenshire and accused Mr Pugh of "washing his hands" of the garden.

Referring to Scotland, England and other European countries, he asked: "Perhaps you can tell us which other nations do not contribute to their national gardens?"

The botanic garden has been in talks with the assembly government - as well as Carmarthenshire Council and the Millennium Commission - to try to secure its future.

Responding to the news, the Millennium Commission - who will call back some of the �21m given to the garden if it is liquidated - said "even at this late hour" they had hope for "viable future for this superb facility."

Meanwhile Carmarthenshire County Council said it was continuing its search for private companies to come to the site's rescue and take it over.

"It's a very sad day for the garden, Carmarthenshire and Wales," said Council Leader Meryl Gravell.

"We were all hoping that the botanic garden would be a huge success. Unfortunately that has not happened."