Danny Alexander has questioned why Scots will have to wait "a thousand more days" before the vote on independence is held.
The chief secretary to the treasury questioned the Scottish Government's preferred date for the poll of autumn 2014 on Friday morning, after First Minister Alex Salmond unveiled his referendum proposals to Holyrood on Wednesday.
Salmond said he wanted to give voters a "short, straightforward and clear" choice by asking them: "Do you agree that Scotland should be an independent country?"
Alexander welcomed the "focus on a single clear question on whether or not Scotland should be independent" today.
He told BBC Radio Scotland's Good Morning Scotland: "I still think there's a question people will want to consider when they respond to these consultations about why it is we have to wait a thousand more days before we can get on and have this question asked.
"I remember back in 2009 when the SNP Government last set out plans for a referendum, they said they were going to call it in 2010. So back then they thought they could get the job done in a year."
Both the Scottish and UK governments are now running consultations on the independence referendum.
The Scottish Government consultation published yesterday revealed its consultation would run until May 11. All responses then have to be analysed, with the the SNP administration due to introduce a Referendum Bill to Holyrood early next year.
This could then be passed by October 2013, and gain Royal Assent the month after that.
But Westminster has said Holyrood does not have the legal authority to stage a ballot on independence, and has offered to temporarily extend its powers to allow a vote to take place.
The Scottish Government has rejected the "strings" Westminster has included in this, although Salmond said on Wednesday he was willing to work with UK ministers to "ensure that the referendum is effectively beyond legal challenge".