Ministers are to review the honours system after a number of leaks left Downing Street embarrassed and risked undermining the process.

The Cabinet Office confirmed yesterday that work was "in hand to review the structure and membership of the honours committees".

The aim was to provide greater transparency and a greater independent input to the honours process "while protecting the confidentiality of individual honours candidates and recipients".

Meanwhile, Britain's most senior medical scientist has threatened to quit after being snubbed for a top honour.

Professor Colin Blakemore had threatened to resign as chief of the Medical Research Council unless more backing was given to him by ministers.

His threat followed the revelation that civil servants had decided his work with animal experiments made him too controversial for the honours list.