One of the most senior figures in UK passenger transport could leave his post if Boris Johnson is elected mayor of London.

Peter Hendy, Transport for London's commissioner, has come under fire in the run-up to the May 1 election. The transport supremo has been accused of helping mayor Ken Livingstone's campaign. Meanwhile, he has been rebuked by Johnson for claiming that London's buses are safe.

According to a report by BBC London last week, Hendy will step down if Johnson ousts Livingstone from City Hall. The report also alleged that other TfL officials, including London Underground managing director Tim O'Toole, will quit if Johnson wins.

An article in the Evening Standard on March 10 revealed emails between Hendy and Simon Fletcher, the mayor's chief of staff. In one email to Fletcher, Hendy asks "is there mileage in refuting Boris's two public transport ideas - [articulated buses] cause death by fire and crushing cyclists, and Routemasters are good?"

TfL defended Hendy's actions. "Misleading statements had been made about the safety of bendy buses," a spokesman said. "Peter Hendy is well known for his robust, factual defence of transport improvements in London."

But Johnson was critical of Hendy's behaviour. "This indicates that TfL is caught up in Ken's political machine which is utterly inappropriate," he claimed.

Johnson meanwhile issued a press statement attacking Hendy for claiming that buses are safe places. "You tell that to the people who have to travel on them every day," said Johnson. "How many times a day does the mayor's transport supremo get on a bus?"

Livingstone recruited Hendy soon after he was elected mayor in 2000. Hendy, who was initially responsible for buses, continues to use the 436 bus to travel between Paddington station and his office on Victoria Street each day.