Boris Johnson faces conflict of interest charge over office

Boris Johnson's London mayoral campaign is receiving financial support from a controversial Japanese company that has clashed with the current mayor Ken Livingstone's office over multimillion-pound plans for development in the capital.

The Guardian has learned that the Shirayama Shokusan Corporation has given the Conservative candidate free use of premises within County Hall, which now forms the headquarters for his campaign. Before the launch, Johnson was renting the space, but for the next four months he will pay nothing for accommodation in the prestigious building, which overlooks the London Eye and the Houses of Parliament.

In 2000, Shirayama offered Livingstone free premises from which to run his independent campaign but he rejected the offer, fearing that this might later bring about a potential conflict of interest.

Three years later Shirayama unveiled plans for a multimillion-pound redevelopment close to County Hall but they were blocked by the local authority and then dismissed by Livingstone because it would have involved development on designated metropolitan open land.

Use of the offices in County Hall is worth at least £12,000 based on the preferential rate Johnson had earlier been paying. The arrangement is controversial because if he wins, any future planning application by Shirayama could wind up on his desk.

Shirayama has made known its interest in developing a conference centre in the heart of London.

Planning decisions in London are taken by the boroughs in the first instance but the mayor's approval is usually required for projects of significance and he has the power to overturn councillors' decisions.

The Shirayama donation will help the Johnson campaign reach its target of £1.25m in what has become an increasingly bitter race for the mayoralty. Despite a welter of recent criticism and claims that he has abused his office, Livingstone's lead over his Conservative challenger has stretched to four points, according to a YouGov/ITV poll.

Speaking to the Guardian at the World Economic Forum in Davos yesterday, Livingstone said he would almost certainly run for a fourth term should he again win the capital's vote in May.

"All my instincts are to say yes. My decision will be based on what the opinion polls say, on family commitments and on how I feel," the mayor said.

The revelation about Shirayama is likely to focus attention on funding for the Johnson campaign, which confirmed the gift of the use of County Hall last night. "County Hall offered it to us directly and we decided to take it up because there was no conflict and no planning application pending," a spokesman said.

Johnson has raised £243,000 to stand for mayor of London, with cash coming from some of the wealthiest Conservative supporters in the country. This puts him well ahead of Livingstone and the Liberal Democrat candidate, Brian Paddick. Among the main donors are John Beckwith, who co-founded the London & Edinburgh Trust, a huge property empire, and is now chairman of the private investment company Pacific Investments plc. He has given £50,000.

The former Tory treasurer Lord Marland, a businessman and art collector, has given £15,000. He is in charge of the Johnson campaign and its treasurer. Marland said: "These are just the first donors. I plan to raise £1.25m and there will be some big surprises among those who are going to support Boris."

Paddick said: "Boris Johnson's decision to accept this lucrative offer from the Shirayama Corporation shows very poor political judgment. His minders should know there is no such thing as a free lunch even if he doesn't.

"With serious questions being asked about Ken Livingstone's administration and Boris putting himself 'on offer' in this way, there is only one major candidate Londoners can have absolute trust in."