Thousands of people could be contacted and asked which way they meant to vote in last week's election under a landmark legal challenge.

Lawyers plan to submit papers at the Court of Session challenging the result of the regional list ballot in Glasgow, where around 9000 votes were discarded.

It has also emerged Labour Party lawyers will ask for a manual recount of all the votes cast in the Cunninghame North constituency, which they lost by just 48 to the SNP.

Mike Dailly, a solicitor at the Govan Law Centre, said yesterday he had been contacted by several voters in Glasgow since Friday who believe their votes were among those disregarded.

He said they had wrongly placed two crosses on the regional ballot and none at all on the constituency form.

Mr Dailly said that if the votes had stood, it could have resulted in a seat for Tommy Sheridan's Solidarity Party or another MSP for the Greens and a different national result.

He said: "What we've got in Glasgow is a situation where people who cast their vote have had their vote discounted.

"This is quite important because if a number of those had gone to Tommy Sheridan or the Greens, then clearly that could have meant a different result on the Glasgow list.

"Obviously, given the balance of power, this is hugely important."

Mr Dailly said he planned to raise his legal challenge under Article 3 of the first protocol of the Human Rights Act, which guarantees that citizens should have the conditions in which to express freely their views in an election.

He said he would be looking for two possible outcomes from the legal challenge. "We can either rerun the Glasgow list election, or the returning officer can contact those 9000 people and ascertain their clear intention," he said.

Mr Dailly said contacting each of the voters would be possible because the number of the ballot paper is written beside their name when they turn up to vote.

Last night, Tommy Sheridan told The Herald he was supporting Mr Dailly's case.

He said: "It was a farce. People have expressed their opinion legitimately, but the ballot paper being so complicated wasn't their fault."

A spokesman for the Greens, which has submitted a Freedom of Information request to every returning officer in the country asking for copies of every discarded ballot paper, said they would "watch with interest" Mr Dailly's legal challenge.

The Herald revealed on Saturday that Labour officials in Ayrshire were considering a legal challenge into the result in Cunninghame North where Kenneth Gibson of the SNP narrowly defeated Labour's Allan Wilson, former Deputy Lifelong Learning Minister.

At the heart of the challenge is Labour's claim that Ian Snodgrass, the returning officer at the count, had turned down their request for a manual recount of all the ballot papers.

Allan Wilson said yesterday: "The prospective challenge arises from concerns that have been expressed to me by local party members, and more importantly local people, about the conduct of the ballot in Cunninghame North."

Mr Wilson also rejected accusations by the SNP that the potential legal challenge was "sour grapes" on Labour's part, adding: "Everybody understands a manual recount could even increase the SNP majority."

Mr Snodgrass, who is also chief executive of North Ayrshire Council, said: "We've had no contact whatsoever with Mr Wilson since the election. If he contacts us we will give careful consideration to all his concerns."