Philip Hammond has refused to rule out the EU referendum taking place within six weeks of Scottish, Welsh and other elections in May.
The Foreign Secretary said the law outlining the referendum on the United Kingdom's future membership of the EU does not prevent a vote taking place within a six-week period near the May 5 elections - which also take place in England and Northern Ireland.
Alex Salmond, the SNP's international affairs and Europe spokesman, warned it would be "disrespectful" for such a situation to emerge.
Mr Hammond reiterated MPs will decide the date of the referendum as they will vote on legislation outlining this detail.
Prime Minister David Cameron hopes a deal will be reached on Britain's negotiation demands by February and signalled earlier this month that a referendum will take place at least three months after this agreement.
Speaking in the Commons, Mr Salmond told Mr Hammond: "As I understand it, the Prime Minister has called for a united, harmonious and mutually respectful debate within the Conservative Party on the issue of Europe.
"So in a united, harmonious and mutually respectful way, can I ask you to confirm that a referendum could not be held within six weeks of the date of the Scottish, Northern Irish, London and Welsh elections?
"To do so would both be disrespectful to the decision of this House and also disrespectful of the people engaging in these elections."
Mr Hammond replied: "As you know, that is not what the Bill provides for.
"But given the timescales involved and given the fact we now expect that the conclusion will be reached at the February European Council, I think you can be confident that it will not be possible to hold a referendum before the date of the Scottish elections that you refer to."
Mr Salmond continued to the Conservative frontbencher: "Can I put it to you that if the referendum was held within six weeks after the date of the elections then the two campaign period would intersect, with all the complications that would arise.
"Therefore can I ask you, again, will the date of the referendum be at least six weeks after the date of the Scottish, Welsh and Northern Irish elections?"
Mr Hammond replied: "Well, what I've tried to convey to you is that is not what the Bill provides for - the Bill does not place any prohibition on a referendum being held in that period.
"But ultimately it will be a decision of this House because the date will be decided by (a statutory instrument) brought before this House."
Mr Hammond later insisted he could not guarantee the renegotiation of free trade agreements with the UK - currently in place due to the EU - would be a priority for other countries should Brexit occur.
Shadow Europe minister Pat Glass said people backing a British exit from the EU have "made much of the unrealistic argument" that the country can walk away and "magically retain" trade agreements currently in place due to EU membership.
The Labour frontbencher asked Mr Hammond to assess the impact on British industry and business of the country having no say in future EU regulations, adding: " In other words, what will out look like for British industry and British jobs?"
Mr Hammond replied: "We are clear that Britain benefits from access to the single market, that if Britain voted to leave the European Union we could not be guaranteed access to the single market.
"Britain benefits from the free trade agreements that have been negotiated by the European Union with third countries, we could not guarantee that renegotiating such agreements with the United Kingdom would be a priority for all of those third countries if we were outside of the European Union.
"But in the end this is a balancing act. There has to be a proper calculation made between the costs and the benefits of membership.
"And what we're trying to do in this negotiation is decisively alter that balance in favour of British membership so that we can convince the British people that that's the right future for Britain."
Labour former minister David Hanson ( Delyn) said he believes Mr Cameron will recommend a Yes vote and a referendum, adding: "Why doesn't he just get on and do it now, set a date, face up to his backbenchers and promote the European Union for the good of Britain?"
Eurosceptic Conservative David Nuttall (Bury North) said: "Many people are suspicious of the seriousness of this renegotiation when three of these so-called demands were accepted without any renegotiation at all.
"Why, for example, did the Government bother to ask for a cut in red tape and for more competitiveness when in European Council after European Council in recent years the European Council has made it clear that's exactly what they intended to do anyway."
In reply, Mr Hammond said the UK is seeking an "institutional restructuring that cements these arrangements for the future".