Larry O'Brien's criminal trial begins May 4. (CBC)

Mayor Larry O'Brien will step aside at the beginning of May to prepare for his criminal trial, Ottawa city council agreed Wednesday.

Councillors approved O'Brien's leave, which begins May 2, at a council meeting.

The trial follows an investigation after former mayoral candidate Terry Kilrea swore in an affidavit that O'Brien had offered to pay for his campaign expenses if Kilrea dropped out of the 2006 election campaign.

Terry Kilrea also alleged that O'Brien had said he would help him get a job on the National Parole Board if Kilrea left the race.

O'Brien was charged in December 2007 with pretending to have influence over the government of Canada or a minister of the government, contrary to Sec. 121 of the Criminal Code.

He was also charged with negotiating an appointment, influencing or negotiating appointments or dealing in offices, contrary to Sec. 125 of the Criminal Code.

O'Brien's trial begins May 4.

In the same meeting, council also approved a rotating list of deputy mayors who will have "all the rights, power and authority" of the mayor during O'Brien's absence.

Diane Deans, the councillor for Gloucester-Southgate, will take the reins at city hall for the first few days and be followed by Michel Bellemare, the councillor for Beacon Hill-Cyrville.

Bellemare is expected to fill in for the mayor during the bulk of O'Brien's leave.

If O'Brien is still absent on July 8, council ruled, the councillor for Osgoode, is next in line.

Council also agreed on another backup plan. If both the deputy mayor and the next person in the rotation are away, they said, Gord Hunter, the councillor for Knoxdale-Merivale, will be granted signing powers.

Council said Hunter was chosen because he had agreed not to leave town over the summer.