Nearly a million pounds could be clawed back from Croydon Council's controversial proposed sell-off of precious artworks.

The Heritage Lottery Fund (HLF) warned it may attempt to reclaim some or all of £934,000 investment in the borough's museum service if the sale of 24 Chinese dynasty antiques cost the service its accredited museum status.

Key groups including Arts Council England, Greater London Authority's culture team, industry body the Museums Association and the HLF have been united in condemnation of the proposed sale of the Riesco collection.

Croydon Council said the sale will raise £13m to fund refurbishment of Fairfield Halls.

The Museum of London and Croydon’s Local Studies Forum have also expressed concerns about the plans, which would see the Chinese dynasty antiques bequeathed to the borough by Raymond Riesco in 1964 go under the hammer.

The council wants to cash in on the items as soon as possible before boom in the market for Chinese art ends.

But organisations warned the sale would fall below the museums industry's expected standards and breach the Museums Association's ethical code.

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A porcelain vase, left, from the Kangxi period (1662-1722) and a porcelain pilgrim bottle from the Xuande period (1426-35) could be sold

Arts Council England would be likely to strip the council of its accredited museum status, weakened its chances of receiving future funding.

Some of the Riesco collection - which spans from Neolithic times to the 19th century - is on display at the Croydon Clocktower, although the 24 items proposed for sale have been removed.

Croydon Council claims it would require "Louvre-style security" to display them and pointed out visitor numbers -  which it said totalled 10,000 annually - had not declined since it withdrew the prize items from display.

It insisted Fairfield Halls - which hosts 300,000 visitors a year - were more culturally and economically valuable to the borough than the Riesco collection, which it said had "no intrinsic heritage connection to Croydon".

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A 14th-century stoneware narcissus bowl

The council claimed there were "exceptional circumstances" that justified the sale.

But respondents to its consultation, which closed earlier this month, disagreed.

Just one respondent was in favour of the sale, which arts groups warned would erode public confidence in the council and damage the public sector's cultural reputation.

Nick Merriman, the convenor of the Museums Association’s ethics committee, said: "The council should follow the formal procedure according to the code of ethics. At the moment it is not clear to us that they are doing so.

The council's corporate services committee, which meets on Wednesday, is expected to recommend the sale goes ahead.