It would be a mistake for David Cameron to stage a referendum on the UK's European Union membership in June, Scotland's First Minister has warned.
Nicola Sturgeon said the move would also be "disrespectful" to Scottish, Welsh, Northern Irish and London mayoral elections, which are taking place in May.
Speaking on the BBC's The Andrew Marr Show, Ms Sturgeon also said she also fears that the campaign to keep the UK in Europe will lose if it behaves in the same way as the No campaign during the Scottish independence referendum.
The Prime Minister is currently negotiating a package of EU reforms with other European leaders, with speculation he could hold an in-out vote as early as June if a deal can be agreed at the February European Council.
Commenting on the possible June vote, Ms Sturgeon said: "I think it would be a mistake for David Cameron.
"Two reasons why I would not be in favour of a June referendum.
"One, you might interpret as being a bit selfish. The Scottish election is in May, indeed the Welsh, Northern Irish, London elections are in May.
"I think to have a referendum campaign starting in parallel would be disrespectful to those important elections."
She added: "The second reason is I think it would be better for David Cameron to leave more time between - if he does get a deal at the February European Council - to leave more time between that deal and the point of decision.
"One of the big problems I see for the In campaign at the moment is that as far as David Cameron is concerned it is very much focused on these narrow issues of renegotiation, when in actual fact, if the In campaign is going to prevail, this is going to have to become a positive in principle campaign about why it is better for the UK to stay within the European Union."
Ms Sturgeon continued: "While there are differences between the Scottish campaign and a European referendum, there are undoubtedly analogies. If the In campaign behaves the way the No campaign behaved in the Scottish referendum I fear it will lose."
Conservative former Cabinet minister Sir Eric Pickles, said it was better to have "some control" inside the EU than be outside and have none.
He told Murnaghan on Sky News: "In terms of the single market, in terms of all the things that go with that we would be tremendously affected by (being) outside. I think it is better to have some control inside than to go out."
Conservative Bernard Jenkin dismissed suggestions giving Britain an emergency brake on migration would be a good outcome for David Cameron's renegotiations ahead of the referendum.
He told BBC Radio 4's World This Weekend: "We are so obviously in a panic period now trying to dress up the outcome of this renegotiation as something when it is likely to be virtually nothing.
"Whatever is decided at this renegotiation because there is going to be no treaty change that is binding upon the other member states, the law of the European Union will not actually have changed.
"And, once we have voted in a referendum to remain, if we do, there is absolutely nothing to stop the European Union tearing up whatever's agreed and going back to what there was before."
Former minister Nick Herbert, who led the campaign to keep Britain out of the euro 15 years ago but has now launched the Conservatives for Reform in Europe (CRE) group, told the programme the idea of a brake was "worth looking at".
He told the programme: "What Conservatives will be interested in is the overall package and what that achieves in terms of our ability to reduce very high levels of net migration."