One of the people leading Southampton City Council's plans to develop a new museum will be leaving the service in the new year.

Janet Owen, the council's arts and heritage manager, has been appointed head of museums, arts and the South East Hub at Hampshire County Council. She will take up the post in January.

Southampton council has been criticised for its plans to sell art from its collection to fund the proposed £28m Sea City Museum. In September, the Museums Association's ethics committee ruled that selling the artworks was "premature", as all other funding avenues had not been exhausted.

The committee also said that it was unclear whether the two works identified for sale, After the Race by Sir Alfred Munnings and a Rodin sculpture, were part of the core collection.

Questions have been raised about the future revenue funding for the new museum. A council spokesman said there was a significant revenue commitment from the council to the cultural quarter and the new museum, which he said would amount to well over £1m a year.

"With respect to the new museum, we continue to refine the design and the business plan as the scheme develops, which will determine any additional funding requirements, should that be necessary," he said.

The council spokesman added that it had already been successful in securing grants from Arts Council England and the European Union.

But Stephen Snoddy, director of the New Art Gallery Walsall and an opponent of the sale, said that it was "wholly unrealistic" that there was no firm commitment to increased revenue funding from the council for the new museum.

"While discussions have concentrated on how the capital monies are raised for the new museum, it seems that the other half of the debate has been forgotten - the revenue needed to operate the venue when it opens," he said.