A former Nigerian oil minister accused of being treated to luxury home stays and lavish spending sprees in the UK in exchange for granting government contracts has denied asking for or taking bribes. Diezani Alison-Madueke, 65, told Southwark Crown Court on Monday that she had 'tried to push back on corruption' in a country plagued by it since the days it was a British colony.

Several Nigerian businessmen are alleged to have bankrolled huge spending sprees, including more than £2m at luxury store Harrods and £4.6m on refurbishing homes in London and Buckinghamshire. But the ex-minister said that the cost of services laid on for her while on official duties were later repaid. 'I can state categorically that at no point did I ask for, take or receive a bribe of any sort from these persons and did not abuse my office,' Alison-Madueke told the court. 'I always sought to act impartially.'

She said money spent on her behalf was reimbursed by the state-owned Nigerian National Petroleum Company (NNPC), adding that a service company was set up in London to handle the logistics because the financial structure of the NNPC was in a mess. 'They paid for all my hotels, chauffeurs... to allow me to perform the job that I did,' she said.

The prosecution's case is based on allegations that Alison-Madueke was given access to a 'grand' home in Buckinghamshire, a £2.8 million home in Marylebone, and multi-million pound homes overlooking Regent's Park, and allegedly benefited from renovations valued at £4.6m. The court heard how she and her extended family spent five days over Christmas 2011 at a house in Gerrards Cross, Buckinghamshire, because her ex-husband required hospital treatment and could not fly back to Nigeria. She said she was not involved in the arrangements for the stay.

A second visit, she said, was over two weeks when she and 10 to 12 officials wrote a book praising the Nigerian president's championing of women. 'I took it upon myself to put together that book to showcase what he did for women,' she said.

Alison-Madueke denies five counts of accepting bribes and a charge of conspiracy to commit bribery. The trial continues.