The Department for Transport (DfT) is being investigated over allegations it deleted sensitive emails about the expansion of Heathrow airport, it has been emerged.
Conservative MP Justine Greening asked for an investigation after she used the Freedom of Information Act to obtain emails sent between the DfT and airport operator BAA.
The MP said there were gaps in the email exchanges, which took place between September and November 2007, when the Government was looking at plans for a controversial third runway.
It is a criminal offence to delete or conceal records to prevent them from being disclosed under the Freedom of Information Act.
Ms Greening told the Sunday Times one email sent between the DfT and BAA on November 1, 2007, referred to potentially damaging information and asked: "Can we play down?"
The reply was among the emails to have allegedly disappeared.
Ms Greening, who has led the campaign against the £9 billion expansion, told the newspaper: "I have been trying to obtain these crucial discussions about the Heathrow consultation for nearly two years.
"When they were released it was clear that some of the material was missing.
"The deletion of these emails could be a criminal offence and I am very pleased that the Information Commissioner is investigating."
She said the ICO had notified her in writing to say it was planning "quite an intensive investigation in a short timescale with the limited resources available to our office".