Voters are now more likely to base their vote on the state of the NHS than they are about Brexit with less than a month to go before election day, a new poll has found.

In a major boost for Labour the long-running Ipsos MORI tracker recorded large jumps in concern about the NHS and public services generally over recent weeks.

The NHS is now solidly ahead of Brexit as a concern, with 60 per cent of voters citing the issue in the poll conducted 15-18 November, up 6 per cent compared to a similar poll conducted 8-11 November.

For comparison 56 per cent of voters thought Brexit or the EU was an important issue in helping them decide how to vote, up 1 per cent compared to the last poll.

Crucially, the poll was conducted before a head-to-head debate between Jeremy Corbyn and Boris Johnson on Tuesday in which the future of the NHS came to the fore as a key issue. Mr Corbyn accused the prime minister of wanting to give US healthcare firms access to the UK service as part of a trade deal with Donald Trump.

The winter date of the election means the health service will be under particular strain during the campaign period, with observers warning of a "winter crisis". Last year's was officially the worst on record, according to an analysis verified by the House of Commons Library.

British Medical Association chair Dr Chaand Nagpaul said earlier this month that staff and patients had endured "winter after winter of overcrowded emergency departments, long delays and pitifully low staffing levels" under the Tories' watch, adding that "it should not take an election to take stock of just how bad the situation has become".

Public services in general on 28 per cent were also climbing the ranking fast, up 5 per cent, with managing the economy and immigration up 4 per cent each.

Other top issues that people said would decide their vote were social care, crime, and climate change, which all have 30 per cent or more of voters' attention.

Despite the terrain info the election apparently shifting to Labour's advantage, most poll trackers still show the Tories with around a 10 point lead over the opposition.

The two main parties are due to launch their manifestos over the next week, with Labour's due on Thursday's and the Tories' expected at the weekend. The Lib Dems presented theirs to the public on Wednesday, focusing on Brexit.

Top 10 marginal seats to watch at the general election Show all 10 1 /10 Top 10 marginal seats to watch at the general election Top 10 marginal seats to watch at the general election North East Fife Currently held by the SNP with a majority of 2 Getty Top 10 marginal seats to watch at the general election Kensington Currently held by Labour with a majority of 20 Getty Top 10 marginal seats to watch at the general election Perth and North Perthshire Currently held by the SNP with a majority of 21 Getty Top 10 marginal seats to watch at the general election Dudley North Currently held by independent, formerly Labour, MP Ian Austin with a majority of 22 LivingInMediocrity Top 10 marginal seats to watch at the general election Newcastle-under-Lyme Currently held by Labour with a majority of 30 Derek Harper Top 10 marginal seats to watch at the general election Southampton Itchen Currently held by the Conservatives with a majority of 31 Rob Candish Top 10 marginal seats to watch at the general election Richmond Park Currently held by the Conservatives with a majority of 45 Robin Webster Top 10 marginal seats to watch at the general election Crewe and Nantwich Currently held by Labour with a majority of 48 Jaggery Top 10 marginal seats to watch at the general election Glasgow South West Currently held by the SNP with a majority of 60 Alec MacKinnon Top 10 marginal seats to watch at the general election Glasgow East Currently held by the SNP with a majority of 75 Christine Johnstone

Labour has already pledged to increase funding on the NHS and remove elements of privatisation from the service. The NHS budget would rise to £155bn by 2023-24 – around £6 billion more than the Conservative government promised for front-line services when it announced its funding settlement last year.