The former governor of one of Nigeria's richest oil-producing states was jailed for 13 years today after admitting fraud totalling nearly £50 million.

And the £50 million figure may prove to be "ludicrously low", said Judge Anthony Pitts as he sentenced Ibori for a series of offences including fraud and money-laundering.

"In the light of other matters, perhaps that is a ludicrously low figure and the figure may be in excess of £200 million, it is difficult to tell," he told Southwark Crown Court in London.

"The confiscation proceedings may shed some further light on the enormity of the sums involved."

Ibori pleaded guilty earlier this year to a series of charges linked to the theft of money from the Delta state and fraud involving state-owned shares in a mobile phone firm.

He admitted one count of conspiracy to launder money, five of money-laundering and one of obtaining a property transfer by deception over the theft of more than £25 million while he wasgovernor of the region.

He also pleaded guilty to conspiracy to defraud, conspiracy to make false instruments, and one count of money-laundering linked to a 37 million US dollar (£23 million) share fraud surrounding the sale of shares in Nigerian company V Mobile.

Ibori, whose address in England was given as Primrose Hill in north London, was previously a cashier in a DIY store in Ruislip, west London, before he moved to Nigeria and worked his way up the ranks to become a state governor in 1999.

Prosecutor Sasha Wass told the court that Ibori "deliberately and systematically" defrauded the people whose interests he was elected to represent.

After the hearing, Sue Patten, head of the Crown Prosecution Service central fraud group, said: "During his two terms as governor of Delta State, James Ibori deliberately and systematically defrauded the people whose interests he had been elected to represent.

"The sums involved in the offences to which Ibori has pleaded guilty amount to approximately £50 million, acquired at the expense of the some of the poorest people in the world.

"Combined sentences of 43 years imprisonment have now been imposed on Ibori and those convicted for assisting him, including his sister, his mistress, his wife, his lawyer and others.

"But the work of the CPS continues. The next step will be to enable the courts to make a confiscation order in respect of Ibori's illegal profits.

"Ibori enjoyed a lavish lifestyle, including several substantial properties, a Bombardier Challenger jet aeroplane costing 20 million dollars he was in the process of buying and several vehicles including a Jaguar, a Mercedes Maybach and a Bentley, all funded from the proceeds of his crimes against the people of Nigeria.

"These are just a number of assets that will be considered as part of confiscation proceedings.

"Three million pounds has already been clawed back from his co-defendants and work continues to realise assets to pay towards the confiscation orders imposed on them."

International Development Secretary Andrew Mitchell said: "James Ibori's sentence sends a strong and important message to those who seek to use Britain as a refuge for their crimes.

"Corruption is a cancer in developing countries and the coalition Government has a zero-tolerance approach to it.

"We are committed to rooting out corruption wherever it is undermining development, and will help bring its perpetrators like Ibori to justice and return stolen funds to help the world's poorest."

A Department for International Development spokesman said: "No British aid was compromised, but his crimes have had a devastating effect on his fellow Nigerians as the money was meant to improve the lives of some of the world's poorest people."

Addressing Ibori, Judge Pitts said he could not give judgment on his record as governor of Delta state.

"I accept that there is another side that is a good side to Mr James Ibori the man, and I am sure the governor of Delta state, a side different to the man of corruption, lining his own and his family's pockets with single-minded devotion and determination, as has been described to me by the prosecution.

"I point out once again, it is not for me to judge your governorship and the effect it has had on the Delta state - I leave that to the good people of Nigeria and Delta state themselves."

Ibori, whose age was given as either 50 or 54 during the sentencing, was governor of the state, said to be one of the richest oil producing regions in Nigeria, between May 1999 and May 2007.

As governor, he was racking up credit card bills of 200,000 US dollars (£126,000) per month on a luxury lifestyle, including running a fleet of armoured Range Rovers.

He was trying to buy a plane for £20 million at the time he was arrested.

His wife Theresa Ibori, sister Christine Ibori-Idie, mistress Udoamaka Okoronkwo and London-based solicitor Bhadresh Gohil have already been convicted of money-laundering.

Ibori was extradited from Dubai to the UK in April last year.

The court heard that Ibori had become a multi millionaire after living modestly in London working on the till of DIY store Wickes.

Judge Pitts told Ibori: "You lived modestly in London in the 1990s and noone I think hearing at that time would imagine the multi millionaire high profile governor that you became some eight or nine years later."

Ibori had previously been convicted of two minor thefts - for stealing from the till of Wickes and in 1992 of handling a stolen credit card.

The court heard he allegedly used a false date of birth when he ran for the governorship of Delta state to conceal the previous convictions as a criminal record would have excluded him from taking part in the election.

He was elected governor of the Delta state for two terms spanning eight years from May 1999 to May 2007.

Judge Pitts said: "It was during those two terms that you turned yourself in short order into a multi millionaire through corruption and theft in your powerful position as Delta stategovernor."

Nicholas Purnell QC, for Ibori, highlighted his work as a governor including his contribution to improving the infrastructure of the Delta state.

He added that Ibori had secured the release of foreign oil workers held hostage in Nigeria in 2006 and 2007.

He said: "He was fully engaged in the business of governorship and not simply someone who sought public office in order to enrich himself and his family."

The court also heard from former England footballer John Fashanu, who is ambassador for the federal Government of Nigeria for sports and tourism. Fashanu, who said he has known Ibori for more than 20 years, spoke of Ibori's achievements in creating sporting facilities in the Delta state.