By Harry Peart BBC sports correspondent, Zurich

The general secretary of football's world governing body, Michel Zen-Ruffinen, has included Fifa president Sepp Blatter in his sweeping allegations of mismanagement within the organisation.

In the report - which one member of the executive committee called a bombshell - he raises the possibility that the Fifa president himself is open to criminal investigation.

Blatter has a week to formally respond to the allegations, but he has previously strongly denied any wrongdoing.

Deadline

Zen-Ruffinen accuses Blatter of breaking Fifa rules by taking over the management and administration of the organisation.

The secretary general has produced a range of allegations into Fifa's management, including misleading accountancy practices, evidence of conflict of interest and suggestions that there could be a criminal investigation into some of the activities.

Some actions by Blatter, he states, would constitute a criminal act under Swiss law.

At a news conference after the meeting, Blatter said it was hazardous to talk about a criminal investigation.

But he has only one week to respond to the allegations of the general secretary, who is a former lawyer and has legal responsibility for the running of Fifa and its finances.

Critical time

There has been a wealth of speculation following the collapse of Fifa's marketing partner, ISL.

Blatter claims it has cost the football organisation $30m - his critics say it could be 10 times more.

The uproar could not have come at a more critical time.

An election campaign is in progress, with Blatter facing the challenger, Issa Hayatou of Cameroon.

And the vote is coming two days before the start of the World Cup in just over three weeks' time.