Latest EU referendum poll of polls: Remain holds lead as Sir John Major and Tony Blair join forces

With just 14 days to go until the big vote, YouGov's rolling seven-day average of polls shows it is still neck and neck between Remain and Leave.

The average contradicts our latest week-long poll which closed with 35,731 entries - of which 71 per cent said they intend to vote Leave, 27 per cent said Remain and two per cent were undecided.

• Vote in our new poll here:

Today a Tory MP switched to the Remain camp in protest at Leave claims on the NHS and former prime ministers Sir John Major and Tony Blair shared a platform to warn that leaving the EU would be a "historic mistake" which could threaten Northern Ireland's peace process.

Commons Health Select Committee chairwoman Sarah Wollaston switched sides and hit out at the Brexit claim that withdrawal would hand the NHS an extra £350 million a week.

The Totnes MP said she was changing sides because she was not comfortable with the claim being on the side of the Brexit battle bus.

Dr Wollaston told the BBC: "For someone like me who has long campaigned for open and honest data in public life I could not have set foot on a battle bus that has at the heart of its campaign a figure that I know to be untrue."

Dr Wollaston warned there would be a "Brexit penalty" on the NHS as withdrawal would damage the economy.

"The consensus now is there would be a huge economic shock if we voted to leave. Undoubtedly, the thing that's most going to influence the financial health of the NHS is the background economy. So I think there would be a Brexit penalty."

Former adversaries Sir John Major and Tony Blair shared a platform at the Ulster University's Magee campus in Londonderry, and warned that Brexit could lead to the break-up of the UK.

Sir John said: "I believe it would be an historic mistake to do anything that has any risk of destabilising the complicated and multi-layered constitutional settlement that underpins stability in Northern Ireland."

Both men played crucial roles in the Northern Ireland peace process, and Sir John warned that the "wrong outcome on June 23 could "tear apart the UK".

Mr Blair hit out at the Leave campaign, claiming it puts an "ideological fixation" with Brexit ahead of the damage it would cause.

He said: "I say, don't take a punt on these people. Don't let them take risks with Northern Ireland's future. Don't let them undermine our United Kingdom."

Meanwhile election chiefs warned that extending the deadline for registering to vote in the EU referendum poses a risk to the smooth running of the vote.

The Association of Electoral Administrators said the additional work could push already-stretched expert staff to breaking point.

Emergency laws allowing an extra 48 hours to sign up to take part in the June 23 vote have been approved by MPs after the official website crashed close to the original deadline of midnight on Tuesday, shutting out potentially thousands of people.

Ministers have promised to provide additional resources to help local councils deal with the extra workload.

But AEA chief executive John Turner questioned how useful that help would be and said he feared officers could be overwhelmed.

"The risk is that this will divert staff away from other critical tasks they should be pursuing," he said - noting that the period for processing the applications and dealing with objections now ran into the week of the vote itself.

"They have made some suggestions that they will provide extra resources. The problem with that is that additional staff will have to be trained," he told the Press Association.

The Cabinet Office is yet to give any details of the proposed assistance.