Candidates for the north-west ward were called in at a few hours' notice by Electoral Commissioner Warwick Gately to an "urgent" briefing on Melbourne Cup day.

Mr Gately told candidates he was angered and disappointed at the attempt to interfere in the council election.

He said commission staff had noticed a high number of multiple returns in the north-west ward election, and subsequent checking showed hundreds of "suspicious" returned postal voting declarations that did not appear to have been completed by the voter.

The VEC is examining further returns against voter enrolment forms.

"This is a serious matter and carries significant penalties if the investigation verifies the attempt and identifies the person or people involved," Mr Gately said.

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He said he was confident the apparent vote tampering was confined to the north-west ward, after extra checks showed no such activity in other wards.

"By law the VEC must proceed with finalising the count and declaring the result of this election, but I will lodge an application to the Victorian Civil and Administrative Tribunal for an inquiry into the election for north-west ward as soon the result is declared."

The VEC has asked anyone with information about the suspected vote tampering to call Crime Stoppers on 1800 333 000.