Douglas Alexander, Scottish Secretary, yesterday struggled to defend the government's role in the Holyrood voting fiasco as he faced a call for his resignation from the SNP in the Commons.

Under attack from MPs on all sides of the House, Mr Alexander resisted a full independent inquiry preferring instead to wait for the Scottish Electoral Commission review of the elections which will be published by the summer.

The exchanges came as the LibDems rejected a plea from the Greens to enter talks on the future governing coalition of Scotland.

Nicol Stephen's party had come under pressure to meet the Greens on Thursday to discuss a rainbow coalition involving the SNP, LibDems and the two Green MSPs. A spokeswoman for the Lib- Dems said that it was "politely declining" the offer.

In the Commons, a succession of MPs, including Labour back benchers, questioned the Scottish Electoral Commission's ability to investigate decisions regarding the voting system for which it had been partly responsible.

Mr Alexander said: "Our first obligation is to secure answers. There is a statutory review, which has begun, by the Electoral Commission. I've made clear that where that inquiry touches on matters directly within the responsibility of the Electoral Commission there will be independent assessment."

He acknowledged the concerns about postal ballots; the e-counting machines; and the significant number of spoilt ballot papers - about 100,000 - but he was not prepared to take responsibility for what went wrong.

Outside chamber, Angus Robertson, Moray's SNP MP, said: "The Secretary of State for Scotland refused to answer basic questions during Scottish Questions today. Did he take the final decision on a single ballot paper? Was there any further testing on the design of the ballot paper following that decision and will he publish all ministerial correspondence regarding this issue and his department's role?

"It is ludicrous for the Secretary of State for Scotland to continue to be responsible for Scottish elections, and for the Westminster government to deny that they are indeed responsible. We are calling for him to stand down and for future legislation to fully devolve responsibility for elections held in Scotland to the Scottish Parliament."

The Tories called on Mr Alexander to apologise for the debacle.

David Mundell, Shadow Scottish Secretary, accused Mr Alexander of ignoring repeated warnings about the pitfalls of the introducing the new voting system, new ballot papers and a new method of counting on the same day.

Mark Lazarowicz, Labour MP for Edinburgh North and Leith, said: "There's no doubt that great damage has been done to trust in the political system by the events of last Thursday and Friday."

He argued that local elections should not be held on the same day as the Scottish parliamentary vote in future.

Meanwhile, the firm behind the electronic vote-counting system insisted it was not to blame for the delays which marred the count, which resulted in the SNP winning 47 seats and Labour winning 46.

DRS Data Services said that initial investigations showed that the delays which occurred across the country had nothing to do with their machines.

The company blamed the "unprecedented volume" of spoiled ballot papers, which needed to be checked manually, for the delays, apparently because voters were confused by the use of different voting systems in the parliamentary and council elections.

DRS said that it was able to deliver both sets of results within 24 hours - something it said would have taken days if the counts had been done manually.

In a statement, DRS said five of the 32 counts had been adjourned until Friday morning. "Investigations are under way as to the precise cause of these delays, but at this early stage it appears likely that the unprecedented volume of ballots requiring manual adjudication was the major contributory factor," the statement said. The company added: "DRS would like to make it absolutely clear that the electronic counting process was not responsible for any spoilt ballot papers."