Latest figures released by EMAS reveal it has a £8.74m deficit - 20 times higher than predicted.
The NHS Trust Development Authority, which monitors trusts, said it was working closely with the service to help address financial pressures.
EMAS said it has spent more on extra vehicles, staff, training and overtime payments.
It had predicted an overspend of about £500,000 at the start of the year.
The money problems at EMAS are getting worse.
One of the biggest problems is handover delays to A&E because they're too busy to accept patients straight away.
So far this year, more than 10,000 patients have had to wait more than an hour and because the ambulance service gets paid for each patient it takes to hospital, they are losing out.
Also the NHS would like to treat more people at home, but of course it is a financial disincentive.
Our busiest A&E department at Leicester Royal Infirmary is trying to sort it out, but I don't think there's any quick fix.
EMAS claims it is owed £2.6m in compensation for the handover delays, which has contributed to the overspend.
The deficit could rise as demand for the emergency service traditionally increases in January and February.
Richard Wheeler, director of finance of EMAS, said: "The challenges we face come with an increase in cost, including cost of training and upskilling our frontline staff, given the national shortage in paramedics.
"[Also an] increased cost in providing additional staff and vehicles to cover for staff delayed at hospitals, and also extra payments for shifts which don't finish on time.
"Our five-year business plan... will contribute financially and to future sustainability.
"We will not do anything that will impact negatively on patient safety or care," he added.
A spokesperson for the NHS Trust Development Authority said: "It is a challenging time... and [we] are working closely with EMAS to help them address ongoing pressures around finances."

The 18-year-old scored twice in 15 appearances, mostly from the bench, last season, including the goal that relegated rivals Dundee United.
He spent the first half of the campaign on loan at Raith Rovers, netting once.
"We are looking forward to the continuation of his development over the next three years," manager Paul Hartley told the club website.

The 41-year-old was in the running for the United post in January 2013 a there was fresh contact after Jackie McNamara left the club this week.
"I know there's an interest there," said Pressley, who spent three years as a player with United in the 1990s.
"But I don't want to come back to Scotland at this moment."
Pressley was sacked by Coventry in February after the Sky Blues slipped into the League One relegation zone.
However, the former Scotland defender is determined to succeed in England and has lofty ambitions.
"I have built up a very good reputation in England and I have a burning desire to manage at the elite level," he told BBC Radio Scotland's Sportsound.
"That's not an arrogance. That's a belief. In order to do that, I think you have to manage in a country like England.
"I think the right opportunity will arise for me here over the next coming months."
Pressley cut his teeth in management at Falkirk after a spell as an assistant to Scotland boss George Burley and is sure his grounding in the game will serve him well.
"My first five years in management could not have been more challenging but I wouldn't change them," he added.
"Most managers now want to come in at the highest level but I think you have to do an apprenticeship.
"At Falkirk I had to reduce the playing budget by close to 75% in three years. At Coventry we reduced the playing budget by 60% in two years - that was four years work that we put into two.
"I'm very proud of the work that we did but my next job has got to be one where I'm not asked to tidy a club up.
"I want to have the opportunity to build on somebody else's work and really have a go at it. I think I've earned the right to do that.
"That's why my next job is a very important one."
East Midlands Ambulance Service (EMAS) has overspent by almost £9m so far this financial year.
[NEXT_CONCEPT]
Dundee striker Craig Wighton has signed a new three-year contract, keeping him at Dens Park until the summer of 2019.
[NEXT_CONCEPT]
Steven Pressley thinks the manager's job at Dundee United is "an exceptional opportunity" but says he is not interested in a return to Tannadice.