Former Birmingham City owners David Gold and David Sullivan have taken control of West Ham United.

A 50% holding, valuing the Premier League club at £105m, gives them the final say on all matters at the club.

Sullivan said Gianfranco Zola will remain as Hammers boss and Karren Brady will join as vice-chairman.

"We're taking on a huge task at a club with enormous problems. It will take time for us to turn it around," Sullivan told BBC Radio 5 live.

The deal has been done in Sullivan's name but he and Gold have been named as West Ham's joint chairmen.

Scott Duxbury has stood down as chief executive, with Sullivan and ex-Birmingham managing director Brady taking over the day-to-day running of the club.

Sullivan added: "We have short-term and long-term goals. In the short term, we want to stay in the Premier League and in the long term we would like to be challenging for the top four and the Champions League."

Asked if there was money available for new players as the club looks to pull away from the relegation zone, Sullivan said: "There will be some transfer funds available to the manager this month.

"January is not the best time to buy players - you don't get many bargains - but the club has such an unbalanced squad, players will have to be bought, loaned or acquired.

"Myself and David Gold will be honest with the fans about the books, the imbalance of the squad and the crazy wages the Icelandic owners paid out that has brought the club to its knees.

"But this is an important day for us. For 20 years, this is the club we wanted. The club is now back in the hands of East Enders, people who understand the community and its passion for the Hammers."

The deal concludes a long-running saga over who will succeed CB Holding, which has indicated the club is £38m in debt, as owners of West Ham.

Sullivan, however, said the club had debts of £110m and had "walked a very close line" to administration.

He also revealed in a news conference on Tuesday afternoon some of the borrowing the club had conducted, including using future season tickets sales as capital.

Sullivan confirmed that CB Holding, whose main shareholder is troubled Icelandic bank Straumur, still retains a 50% share in the club but that the new owners had a four-year option to buy them out.

The pair, who hail from the East End of London and Essex, also said they had been in talks with Newham Council about the prospect of West Ham moving to the 2012 Olympics Stadium after the Games.

Other contenders to bid for West Ham's ownership included Lotus F1 chief Tony Fernandes who pulled out of the race on Monday night, while finance firm Intermarket and Italian Massimo Cellino were also interested.

However, Sullivan is still keen for Fernandes - and others - to invest in the club as he and Gold look to attract wealthy investors to the Hammers.

"We have bought 50% and I have an option to buy the other 50%. If they [wealthy fans] want to get involved with West Ham they will be very welcome," he confirmed.

"Anyone who wants to put in £10m or £15m can buy 10 or 15% of the club and come along and join us.

"We will be approaching Tony [Fernandes] in the hope that he will join us in a kind of national unity purchase of West Ham. We will welcome other investors."

Gold and Sullivan, who left Birmingham City in November following Hong Kong businessman Carson Yeung's takeover, had been determined suitors of the Hammers for several months.

They once held shares in the club and have the assets required to deal with its debts, although the size of the task was cast in a fresh light at Tuesday's unveiling.

West Ham had effectively suspended any activity in the January transfer window until the takeover situation is resolved.

Former Chelsea favourite Zola and assistant Steve Clarke took the managerial reins at West Ham in September 2008 following Alan Curbishley's acrimonious departure.

The pair guided West Ham to ninth in the table last season after a sticky start. The Hammers are currently 16th in a season that has been plagued by injuries and off-field distractions.

But Sullivan is confident Italian Zola can turn the club around on the pitch and stated: "West Ham need stability after all the recent upheavals.

"We appointed four managers and parted company with two at Birmingham in 16 years. We believe in our managers and give them the time and support they need."

That will be welcome news to Zola who, speaking on Friday, said: "I know I can do this job but you always have to prove yourself every day.

"I am not going to go to anyone and say 'look, I am doing well'. The results do the talking. If what I am doing is not good enough on the pitch it is right they change."

BBC SPORT