Clare Short is to receive a written warning from the Labour Party, following her claims that British security services bugged the office of UN secretary general Kofi Annan.

The former international development secretary last month called on the prime minister to resign, claiming that there had been a rush to go to war against Iraq.

In response, Tony Blair accused her of undermining the work of the security services, a criticism she promptly rejected.

The decision to issue a written warning was made at a meeting of the backbench parliamentary Labour Party held on Wednesday night.

Labour chairman Ian McCartney had already said that Short had committed a "significant error of judgement", but had warned against making her a martyr by withdrawing the party whip or suspending her completely.

The Birmingham Ladywood MP has already met with chief whip Hilary Armstrong for discussions about her claims that she had seen transcripts of Annan's telephone conversations.

"The chief whip will be writing to Clare Short to reflect the views of Labour's parliamentary committee and remind Clare of her responsibilities under the code of conduct," said a spokesman.