The Scottish secretary has said he will apologise for the Scottish election fiasco if an inquiry lays the blame at the door of the Scotland Office.
Mr Alexander refused to rule out an independent inquiry
But Douglas Alexander told a Westminster debate that blame should not be attributed before the results of an Electoral Commission probe.
More than 180,000 votes were rejected in the Scottish Parliament and local government polls on 3 May.
Opposition parties have called on the UK Government to accept responsibility.
An Electoral Commission review, being carried out under international election expert Ron Gould, is due to be completed by late summer.
But Mr Alexander refused to rule out setting up a completely independent investigation, which both the SNP and Tories have called for, in the future.
He said: "We have never suggested we would not countenance further inquiries but instead argue that, on balance, it is the right course of action to let the statutory review being led by Ronald Gould to report first before deciding on the next steps.
"As secretary of state I, of course, accept responsibility for the actions of the Scotland Office and if this review finds fault with these actions and decisions I will, of course, apologise."
Mr Alexander accused the Tories, who led the Commons debate, of "opportunism" and added: "I believe it is better to await this report and then take decisions informed by its findings and recommendations."
Shadow Scottish Secretary David Mundell said the rejection of 146,097 ballot papers in the Scottish Parliament election and a further 38,341 in local government polls was an "affront to democracy".
He urged Mr Alexander to take responsibility, adding: "We are not calling for elections to be re-run or for the secretary of state's head - not yet anyway.
"We simply want the government to accept responsibility for the debacle on 3 May, apologise for it to Scotland and hold a full and comprehensive inquiry."
Mr Mundell said it was "entirely predictable" that running the parliamentary and council elections on the same day would lead to problems.
"We want to ensure that this ludicrous situation is never allowed to happen again in Scotland or anywhere else in the UK," he added.
Jo Swinson of the Liberal Democrats said Mr Alexander "still hasn't taken full responsibility for this fiasco".
She said the high level of spoiled ballots "undermined the public's faith" in the electoral system.