David Cameron and Nicola Sturgeon
SNP leader and First Minister of Scotland Nicola Sturgeon and David CameronGetty

David Cameron should drop any plans he has of holding the EU referendum in June because it could create "confusion" among hundreds of thousands of voters, the leaders of the Welsh and Scottish governments have warned. The SNP's Nicola Sturgeon and Welsh Labour's Carwyn Jones have addressed their concerns in a letter sent to the prime minister on 3 February.

The document, which is also signed by Sinn Fein MLA and deputy first minister of Northern Ireland Martin McGuinness as well as DUP MLA Arlene Foster, argued that a June date for the historic ballot would be too close to the Scottish, Welsh and Northern Irish assembly elections, which will be held on 5 May.

"We believe that holding a referendum as early as June will mean that a significant part of the referendum campaign will necessarily run in parallel with those elections and risks confusing issues at moment when clarity is required," the leaders wrote.

"Furthermore, it will be virtually impossible for the political parties in our respective territories to plan effectively for, and where appropriate work together on, the referendum campaign while our own elections are in progress."

The letter was made public just minutes before Prime Minister's Questions (PMQs), where Cameron is expected to be grilled by MPs for the first time since European Council President Donald Tusk published his draft EU reform settlement.

The Conservative leader said the proposed measures, including a "red card" for the UK on laws Brussels, represented "substantial progress". But Eurosceptics claimed the proposals were "watered down" and noted that Cameron had failed to secure his planned ban on EU migrants in the UK from accessing in-work benefits.

Instead, Tusk has tabled a so-called "emergency break", which would see the UK apply to Brussels to implement a temporary ban on EU migrants receiving welfare payments. But European Council President Jean Claude-Junker, who praised the "fair" draft deal, told MEPs the measure could only be used in "exceptional circumstances".

The latest opinion poll from YouGov had "leave" four points ahead of "remain". The survey, of more than 1,700 people between 27 and 28 January, put "leave" on 42%, "remain" on 38% and "undecided" on 20%.