Swiss investigators, acting for the attorney-general’s offices, have seized more documents and electronic data from FIFA headquarters in their inquiries into the 2018-2022 World Cup bid scandal.

The haul is understood to include material from the offices of president Sepp Blatter and the secretary general, Jérôme Valcke, who is under scrutiny over a $10m payment from South African World Cup organisers to the former FIFA vice-president Jack Warner. Authorities in the United States have alleged that this payment was a bribe. Valcke, along with Blatter, denies any wrongdoing.

Swiss prosecutors and the FBI are looking into the controversial bidding process for the 2018 tournament, to be played in Russia, and the 2022 World Cup, awarded to Qatar.

Meanwhile, the head of the German FA has called for term limits for the FIFA presidency and suggested the one member, one vote system for FIFA’s 209 associations should be up for discussion. Wolfsgang Niersbach also suggested that preliminary technical reports should be used to remove the weakest candidates for the World Cup.

“If FIFA had deployed this process then Qatar, with the weakest technical evaluation, would not even have reached the vote,” he said.

The pressure on FIFA will grow on Thursday when the European Parliament debates a motion for Blatter to step down immediately.

The motion, which expresses the parliament’s “long-held view” that FIFA is full of “systemic, widespread and persistent fraud and corruption”, says the credibility of football’s governing body will not be restored until Blatter has gone and widespread reforms are instituted.

Blatter has said he would step down once a successor is chosen – likely to be in December.

Meanwhile, the Brazil legend Zico has confirmed he intends to stand for the presidency of FIFA, insisting it is his “duty”.

“It’s sad for our sport to see what is happening in football today – the corruption… and the hard work of many other good people wasted – and I see it as my duty to use my experience and knowledge to try and stand for the presidency,” he said.