Accident and emergency units in England saw 86.7% of patients within four hours in the week ending January 4, failing to meet the 95% target.
The latest NHS England figures follow the quarterly statistics for the last three months of 2014 which showed that 92.6% of patients were seen within the four-hour target, the worst performance for a decade.
The first set of weekly figures issued this year show that for "type 1" major A&E departments, just 79.8% of patients were seen within four hours.
Some 407,239 patients attended A&E in the week to January 4, up by 5.1 % or almost 20,000 attendances on the same week 12 months ago, and an increase of almost 4,000 on the previous week.
The percentage of patients waiting four hours or less from arrival to admission, transfer or discharge was 86.7% - down from 90.5% in previous week and 94.3% in same week last year.
Dr Sarah Pinto-Duschinsky, director of operations and delivery for NHS England, said: "The NHS continues to face unprecedented pressures on its frontline services - with almost 20,000 more A&E attendances than last year - and more than 105,000 people admitted to hospital which is one of the highest figures on record.
"The extra £700 million invested has bought 800 more doctors, nearly 5,000 more nurses, creating over 6,000 more beds.
"Flu is now at its highest peak for the last three winters which is one of the reasons why over the New Year holiday we continued to treat more patients than ever before.
"This means the NHS will continue to be under pressure for the next few weeks. Even at this stage of the winter it is still worth people getting their flu jab if they have not done so, and get advice from their pharmacist for colds, coughs and minor conditions."
The NHS has been at the centre of a bitter political row between Labour and the Tories, and Ed Miliband has promised to draft in extra nurses to help ease pressure on the NHS if he wins the next election - as the Red Cross was drafted in to help hospitals cope with the A&E crisis.
More than a dozen hospitals enacted emergency measures this week while some patients were forced to wait 12 hours for a bed as A&E units struggled to cope.
The British Red Cross charity, which delivers aid in war and natural disaster zones, has used to help transport patients in some areas.
The Labour leader came up with a five-point plan to bolster the service if his party wins May's general election.
He said patients would be given quicker access to family doctors and GPs could also be installed in hospitals to cool pressure on the straining service.
More nurses would be employed to staff the 111 helpline service to put an end to what Labour described as the "computer says go to A&E" approach.
It would also get councils, the NHS and charities to work together to identify people at highest risk of hospital admission and offer them the support while walk-in centre closures would be halted.
Mr Miliband said: "The Tories want to blame the patients - but the NHS is in crisis because of decisions made by David Cameron.
"His Government has made it harder for families to see a GP while cuts in social care have left vulnerable and elderly people at risk.
"Clearing up this mess will require the long term investment only Labour is prepared to make - 8,000 extra GPs, 5,000 more homecare workers, 3,000 more midwives and 20,000 additional nurses.
"But the scale of the current crisis also demands immediate action.
"If I was prime minister we would be taking action now to ease pressure on A&E by helping families see a GP, getting more nurses answering calls to NHS 111, halting the closures of walk-in centres, tackling the scandal of social care, and recruiting former nurses back into the NHS to help deal with staffing pressures."
The British Red Cross has stepped in to transport some patients home after they were discharged from A&E in Sheffield, where Deputy Prime Minister's Nick Clegg is an MP.
Sheffield Teaching Hospitals NHS Foundation Trust said they were currently facing an "unusual demand" and were very busy at this time.
They are using the charity to help transport patients who are fit enough to leave A&E, but the Red Cross is not providing health care to patients, the hospital's duty matron said.
Andy Peers, British Red Cross operations manager for Yorkshire said: "This is the first time we have provided such support in Sheffield - but we have highly trained volunteers and an extensive fleet of ambulance vehicles across the country, used regularly to support NHS ambulance services during both routine work and periods of high demand."
Chancellor George Osborne defended the Tory record on the NHS and said he had pumped extra money into the system.
He said: "There are more people than ever working in our health service, we are treating more people than ever, the people within the health service are doing a brilliant job and we are backing them up with increases in the amounts of money going to the health service.
"That's not something that has been easy to do, we have had to make difficult decisions - as people are aware - elsewhere in government budgets in order to prioritise the health service."
He told BBC Breakfast: "We want to support our NHS and we back the NHS's own plan for its future and that means additional resources, and I've already made a big down-payment on those resources in the last few weeks by putting £2 billion extra in.
"You can't afford to do that if you don't have an economic plan."