The build-up to this week's world cycling championships in Madrid threatens being overshadowed by a bitter power struggle inside the sport's governing body, the International Cycling Union (UCI).

Accusations of electoral irregularities, a round of mutual recriminations and a flurry of legal action have preceded the vote for the UCI presidency which is due to take place on Friday during the world championships.

Incumbent president Hein Verbruggen, who has been in charge of the body since 1993, is facing opposition from dissident members of the UCI to try to ensure that he does not win a fourth term in office.

Verbruggen and Irish candidate Pat McQuaid have announced that they had begun legal proceedings against UCI management committee member Sylvia Schenk of Germany for defamation.

At the same time the UCI has accused Schenk of pursuing a "witch hunt" against them, saying at the end of a lengthy media release on their website that they have always acted with the "utmost transparency".

Schenk, 52, ran ninth in the women's 800 metres at the 1972 Olympics in Munich and is a former president of the German Cycling Federation.

The conflict took a further twist at the weekend. The Spanish Cycling Federation (RFEC), who are supporting their own candidate Gregorio Moreno for the presidency, announced that they had started legal action against Verbruggen in an attempt to unseat the 64-year-old Dutchman as head of the congress that will preside over next Friday's elections.

The Spanish Federation argues that Verbruggen should not continue as president because of what it calls "manipulation of the electoral process" to choose his successor.