The Government has been asked to scrap the West Pier's Grade I listed status.
The West Pier Trust expects to hear today whether its bid for £19.5 million from the Heritage Lottery Fund is successful after the cost of a rebuild rose by £6 million.
But The Argus has learnt that the Noble Organisation, owner of the rival Palace Pier, has mounted a new attack on the renovation plans.
Noble has asked the Department for Culture, Media and Sport (DCMS) to downgrade or even remove the pier's listed status.
If successful, Noble believes it would seriously undermine any claims the pier has to large-scale public funding.
It is the latest attempt by the Gateshead-based firm to scupper the proposed £44 million restoration by the West Pier Trust and London-based developer St Modwen.
Noble insists the pier has unfairly received public money for what it sees as a modern, commercial rebuild rather than an authentic, heritage-driven restoration.
Noble director David Biesterfield said: "The West Pier may theoretically be a Grade I listed pier based on what it was and its history but it certainly isn't any more.
"There's just nothing left. We have made contact with the DCMS to inform them of our intentions but putting together a detailed application will take a little more time.
"Without listed status the whole scheme would have to be looked at again."
English Heritage gave renewed backing to the rebuild last month after considering the damage caused by partial collapses in January last year and fire last March.
Brighton and Hove City Council gave planning permission last February for the restoration of the pier, built by Eugenius Birch in 1866 and given its Grade I listing in 1984.
Last month's English Heritage report said the West Pier was the most important pleasure pier ever built in terms of its engineering design and architectural ambition and as an enduring social symbol of Brighton.
It said: "Repair and reconstruction would allow these significances to be appreciated."
Mr Biesterfield said Noble would challenge the English Heritage verdict because it was not backed up by national planning guidance.
Conservation groups such as Save Our Seafront have protested about the size of the complex which would be built to help finance the pier's restoration.
Public inquiry Noble fears the plan, featuring bars, restaurants and shops, would create unfair competition to the Palace Pier and other leisure venues in Brighton and Hove.
The company has called for Deputy Prime Minister John Prescott to call in the proposed development for a public inquiry.
Chartered surveyors Colliers CRE, in a report for the city council and English Heritage, expressed fears about the viability of St Modwen's costings and proposed rental prices.
The consultants criticised the average rents of £18.25 per square foot and recommended £15 to avoid problems similar to Brighton's Aquarium Terraces, where developers have struggled to find occupiers.
Noble insists the pier's restoration could be financed with a much smaller on-shore complex covering 37,000sqft rather than 112,000sqft.
It also believes the plans fail to live up to the trust's original 1997 document inviting tenders from private developers, which insisted on period-style amusements such as tea dances, actors in costume and a heritage museum.
The West Pier Trust was confident Noble's bid to de-list the West Pier would fail.
General manager Rachel Clarke said: "English Heritage has only just said how the West Pier is the most important pier in the world and must be repaired.
"I hardly think they would even consider allowing it to be de-listed."
A DCMS spokeswoman said: "Any application to de-list will be considered but this one has not yet gone very far in the process."
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